Varying demodulation to avoid interference

ABSTRACT

In a method of interference avoidance for a capacitive sensor device, a transmitter signal is transmitted with a transmitter electrode of the capacitive sensor device. A resulting signal is received with a receiver electrode of the capacitive sensor device. The resulting signal corresponds to the transmitter signal. A first demodulated output is acquired by demodulating the resulting signal in a first way. A second demodulated output is acquired by demodulating the resulting signal in a second way, where the second way and the first way differ. A shift is made from using the first demodulated output for determining positional information to using the second demodulated output for determining positional information. The shift is based at least in part upon an amount of interference.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to and benefit of co-pending U.S.provisional patent application 61/308,864, filed Feb. 26, 2010 andassigned to the assignee of the present non-provisional application,which is herein incorporated by reference in its entirety.

This application claims priority to and benefit of co-pending U.S.provisional patent application 61/369,617, filed Jul. 30, 2010 andassigned to the assignee of the present non-provisional application,which is herein incorporated by reference in its entirety.

This application is related to U.S. patent application Ser. No. ______by Joseph Kurth Reynolds, filed on Feb. 24, 2011, entitled “ShiftingCarrier Frequency to Avoid Interference” with attorney docket numberSYNA-20091207-A1B, and assigned to the assignee of the presentnon-provisional application. To the extent not repeated herein, thecontents of this related patent application are incorporated herein byreference.

This Application is related to U.S. patent application Ser. No. ______by Joseph Kurth Reynolds et al., filed on filed on Feb. 24, 2011,entitled “Sensing During Non-Display Update Time to Avoid Interference”with attorney docket number SYNA-20091207-A1C, and assigned to theassignee of the present non-provisional. To the extent not repeatedherein, the contents of this related patent application are incorporatedherein by reference.

BACKGROUND

Input devices including proximity sensor devices (also commonly calledtouchpads, touch screens, or touch sensor devices) are widely used in avariety of electronic systems. A proximity sensor device typicallyincludes a sensing region, often demarked by a surface, in which theproximity sensor device determines the presence, location and/or motionof one or more input objects. Proximity sensor devices may be used toprovide interfaces for the electronic system. For example, proximitysensor devices are often used as input devices for larger computingsystems (such as opaque touchpads integrated in, or peripheral to,notebook or desktop computers). Proximity sensor devices are also oftenused in smaller computing systems (such as opaque or transparent touchscreens integrated in cellular phones).

SUMMARY

In a method of interference avoidance for a capacitive sensor device, atransmitter signal is transmitted with a transmitter electrode of thecapacitive sensor device. A resulting signal is received with a receiverelectrode of the capacitive sensor device. The resulting signalcorresponds to the transmitter signal. A first demodulated output isacquired by demodulating the resulting signal in a first way. A seconddemodulated output is acquired by demodulating the resulting signal in asecond way, where the second way and the first way differ. A shift ismade from using the first demodulated output for determining positionalinformation to using the second demodulated output for determiningpositional information. The shift is based at least in part upon anamount of interference.

In a method of avoiding interference in an integrated capacitive sensordevice and display device, a first transmitter signal having a firstfrequency is transmitted with a combination electrode of the integratedcapacitive sensor device and display device. The combination electrodeis configured for both capacitive sensing and display updating. A shiftis made from transmitting the first transmitter signal with thecombination electrode to transmitting a second transmitter signal withthe combination electrode. The shift is made by changing a duration ofat least one non-display update time period of the display device. Thesecond transmitter signal has a second frequency, and the shiftingoccurs based at least in part upon an amount of interference.

In a method of capacitive sensing using an integrated capacitive sensordevice and display device, a transmitter signal is transmitted with acombination electrode of the integrated capacitive sensor device anddisplay device. The combination electrode is configured for bothcapacitive sensing and display updating. The transmitter signaltransitions at least twice during a non-display update time periodassociated with row update of the display device. A display of thedisplay device is updated during an update time period. A resultingsignal is received with a receiver electrode of the integratedcapacitive sensor device and display device during the non-displayupdate time period. The resulting signal corresponds to the transmittersignal.

BRIEF DESCRIPTION OF DRAWINGS

The drawings referred to in this Brief Description of Drawings shouldnot be understood as being drawn to scale unless specifically noted. Theaccompanying drawings, which are incorporated in and form a part of theDescription of Embodiments, illustrate various embodiments of thepresent invention and, together with the Description of Embodiments,serve to explain principles discussed below, where like designationsdenote like elements, and:

FIG. 1A is a block diagram of an example input device that is coupledwith an example electronic system, in accordance with embodiments of theinvention;

FIG. 1B shows a portion of an example sensor electrode pattern which maybe utilized to generate all or part of the sensing region of an inputdevice, according to an embodiment;

FIGS. 1C and 1D illustrate different examples of combination electrodes,according to various embodiments;

FIG. 1E shows an example of an input device according to variousembodiments;

FIG. 2 shows an example of a capacitive measuring system configured todemodulate samples of a received resulting signal to improve theinterference susceptibility of a capacitive sensor, according to anembodiment;

FIG. 3A illustrates a waveform of a capacitive sensor using ademodulation frequency that is the same as the frequency of thetransmitted transmitter signal, according to an embodiment;

FIGS. 3B-3D illustrate example waveforms which each have a sensingdemodulation frequency that is different than the frequency of thetransmitted transmitter signal to improve interference susceptibility,according to various embodiments;

FIG. 4 illustrates a first example processing system which may beutilized with an input device, according to various embodiments;

FIGS. 5A and 5B illustrate a flow diagram of an example method ofinterference avoidance for a capacitive sensor device, according tovarious embodiments;

FIG. 6 illustrates a display device comprising a display with aplurality of display rows, according to an embodiment;

FIG. 7 illustrates a second example processing system which may beutilized with an input device, according to various embodiments;

FIG. 8 illustrates a flow diagram of an example method of avoidinginterference in an integrated capacitive sensor device and displaydevice, according to various embodiments;

FIG. 9 illustrates three transmitter signals with transitions duringnon-display update time, according to various embodiments;

FIG. 10 illustrates a third example processing system which may beutilized with an input device, according to various embodiments; and

FIGS. 11A-11C illustrate a flow diagram of an example method ofcapacitive sensing using an integrated capacitive sensor device anddisplay device, according to various embodiments.

DESCRIPTION OF EMBODIMENTS

The following Description of Embodiments is provided by way of exampleand not of limitation. Furthermore, there is no intention to be bound byany expressed or implied theory presented in the preceding Background orSummary, or the following Description of Embodiments.

Overview of Discussion

Herein, various embodiments of the present invention provide inputdevices and methods that facilitate improved usability. In variousembodiments described herein, the input device may be a capacitivesensor device; a capacitive sensor device used in conjunction with orproximate a display device; or an integrated capacitive sensor deviceand display device which share use of one or more components.

Discussion begins with a description of an example input device withwhich or upon which various embodiments described herein may beimplemented. Following this, the discussion is split into threesections. Section 1 discusses varying demodulation to avoidinterference, and describes some techniques for demodulating a resultingsignal differently. A first example processing system and componentsthereof are described in Section 1. Operation of the first processingsystem and its components are further described in conjunction withdescription of an example method of interference avoidance for acapacitive sensor device. Section 2 discusses shifting carrier frequencyto avoid interference, and describes shifting from a first transmittersignal have a first frequency to a second transmitter signal have asecond frequency. A second example processing system and componentsthereof are described in Section 2. Operation of the second processingsystem and its components are further described in conjunction withdescription of an example method of avoiding interference in anintegrated capacitive sensor and display device. Section 3 discussessensing during non-display update time to avoid interference, anddescribes some non-display update time periods and sensing techniques. Athird example processing system and components thereof are alsodescribed in Section 3. Operation of the third processing system and itscomponents are further described in conjunction with description of anexample method of sensing using an integrated capacitive sensor deviceand display device.

Example Input Device

FIG. 1A is a block diagram of an example input device 100, in accordancewith embodiments of the invention. The input device 100 may beconfigured to provide input to an electronic system 150. As used in thisdocument, the term “electronic system” (or “electronic device”) broadlyrefers to any system capable of electronically processing information.Some non-limiting examples of electronic systems 150 include personalcomputers of all sizes and shapes, such as desktop computers, laptopcomputers, netbook computers, tablets, web browsers, e-book readers, andpersonal digital assistants (PDAs). Additional example electronicsystems 150 include composite input devices, such as physical keyboardsthat include input device 100 and separate joysticks or key switches.Further example electronic systems 150 include peripherals such as datainput devices (including remote controls and mice), and data outputdevices (including display screens and printers). Other examples includeremote terminals, kiosks, and video game machines (e.g., video gameconsoles, portable gaming devices, and the like). Other examples includecommunication devices (including cellular phones, such as smart phones),and media devices (including recorders, editors, and players such astelevisions, set-top boxes, music players, digital photo frames, anddigital cameras). Additionally, the electronic system 150 could be ahost or a slave to the input device.

The input device 100 can be implemented as a physical part of theelectronic system 150, or can be physically separate from the electronicsystem 150. As appropriate, the input device 100 may communicate withparts of the electronic system 150 using any one or more of thefollowing: buses, networks, and other wired or wirelessinterconnections. Examples include, but are not limited to:Inter-integrated Circuit (I²C), Serial Peripheral Interface (SPI),Personal System 2(PS/2), Universal Serial Bus (USB), Bluetooth®, RadioFrequency (RF), and Infrared Data Association (IrDA).

In FIG. 1A, the input device 100 is shown as proximity sensor device(also often referred to as a “touchpad.” or a “touch sensor device”)configured to sense input provided by one or more input objects 140 in asensing region 120. Example input objects include fingers and styli, asshown in FIG. 1A.

Sensing region 120 encompasses any space above, around, in and/or nearthe input device 100 in which the input device 100 is able to detectuser input (e.g., user input provided by one or more input objects 140).The sizes, shapes, and locations of particular sensing regions may varywidely from embodiment to embodiment. In some embodiments the sensingregion 120 extends from a surface of the input device 100 in one or moredirections into space until signal-to-noise ratios prevent sufficientlyaccurate object detection. The distance to which this sensing region 120extends in a particular direction, in various embodiments, may be on theorder of less than a millimeter, millimeters, centimeters, or more, andmay vary significantly with the type of sensing technology used and theaccuracy desired. Thus, some embodiments sense input that comprises nocontact with any surfaces of the input device 100, contact with an inputsurface (e.g., a touch surface) of the input device 100, contact with aninput surface of the input device 100 coupled with some amount ofapplied force or pressure, and/or a combination thereof. In variousembodiments, input surfaces may be provided by surfaces of casingswithin which the sensor electrodes reside, by face sheets applied overthe sensor electrodes or any casings, a lens window for a display, etc.In various embodiments, an air gap may exist between a face sheet andthe sensor electrodes. In some embodiments, the sensing region 120 has arectangular shape when projected onto an input surface of the inputdevice 100. In some embodiments, the sensor region may comprise multiplesub regions that may be used for determining two-dimensional positionalinformation for at least one input object, determining one-dimensionalpositional information for at least one input object andzero-dimensional positional information for at least one input object.The configuration of sensing regions and responses may be dynamic and/ordependent on user input, external communication or based on processingsystem 110.

The input device 100 may utilize any combination of sensor componentsand sensing technologies to detect user input in the sensing region 120.The input device 100 comprises one or more sensing elements fordetecting user input. As several non-limiting examples, the input device100 may use capacitive, elastive, resistive, inductive, surface acousticwave, and/or optical techniques.

Some implementations are configured to provide images that span one,two, three, or higher dimensional spaces. Some implementations areconfigured to provide projections of input along particular axes orplanes.

In some capacitive implementations of the input device 100, voltage orcurrent is applied to create an electric field. Nearby input objectscause changes in the electric field, and produce detectable changes incapacitive coupling that may be detected as changes in voltage, current,or the like.

Some capacitive implementations utilize arrays or other regular orirregular patterns of capacitive sensing elements to create electricfields. In some capacitive implementations, separate sensing elementsmay be ohmically shorted together to form larger sensor electrodes. Somecapacitive implementations utilize resistive sheets, which may beuniformly resistive.

Some capacitive implementations utilize “self capacitance” (or “absolutecapacitance”) sensing methods based on changes in the capacitivecoupling between sensor electrodes and an input object. In variousembodiments, an input object near the sensor electrodes alters theelectric field near the sensor electrodes, thus changing the measuredcapacitive coupling. In one implementation, an absolute capacitancesensing method operates by modulating sensor electrodes with respect toa reference voltage (e.g., system ground), and by detecting thecapacitive coupling between the sensor electrodes and input objects.

Some capacitive implementations utilize “mutual capacitance” (or“transcapacitance”) sensing methods based on changes in the capacitivecoupling between sensor electrodes. In various embodiments, an inputobject near the sensor electrodes alters the electric field between thesensor electrodes, thus changing the measured capacitive coupling. Inone implementation, a transcapacitive sensing method operates bydetecting the capacitive coupling between one or more transmitter sensorelectrodes (also “transmitter electrodes” or “transmitters”) and one ormore receiver sensor electrodes (also “receiver electrodes” or“receivers”). Transmitter sensor electrodes may be modulated relative toa reference voltage (e.g., system ground) to transmit transmittersignals. Receiving sensor electrodes may be held substantially constantrelative to the reference voltage to facilitate receipt of resultingsignals. A resulting signal may comprise effect(s) corresponding to oneor more transmitter signals, and/or to one or more sources ofenvironmental interference (e.g., other electromagnetic signals). Sensorelectrodes may be dedicated transmitters or receivers, or may beconfigured to both transmit and receive.

In FIG. 1A, a processing system (or “processor”) 110 is shown as part ofthe input device 100. The processing system 110 is configured to operatethe hardware of the input device 100 to detect input in the sensingregion 120. The processing system 110 comprises parts of or all of oneor more integrated circuits (ICs) and/or other circuitry components; insome embodiments, the processing system 110 also compriseselectronically-readable instructions, such as firmware code, softwarecode, and/or the like. In some embodiments, components composing theprocessing system 110 are located together, such as near sensingelement(s) of the input device 100. In other embodiments, components ofprocessing system 110 are physically separate with one or morecomponents close to sensing element(s) of input device 100, and one ormore components elsewhere. For example, the input device 100 may be aperipheral coupled to a desktop computer, and the processing system 110may comprise software configured to run on a central processing unit ofthe desktop computer and one or more ICs (perhaps with associatedfirmware) separate from the central processing unit. As another example,the input device 100 may be physically integrated in a phone, and theprocessing system 110 may comprise circuits and firmware that are partof a main processor of the phone. In some embodiments, the processingsystem 110 is dedicated to implementing the input device 100. In otherembodiments, the processing system 110 also performs other functions,such as operating display screens, driving haptic actuators, etc. Insome embodiments, the electronically-readable instructions of processingsystem 110 may be updated by electronic system 150, where electronicsystem 150 may update the electronically-readable instructions ofprocessing system 110 via wired and wireless communications.

The processing system 110 may be implemented as a set of modules thathandle different functions of the processing system 110. Each module maycomprise circuitry that is a part of the processing system 110,firmware, software, or a combination thereof. In various embodiments,different combinations of modules may be used. Example modules includehardware operation modules for operating hardware such as sensorelectrodes and display screens, data processing modules for processingdata such as sensor signals and positional information, and reportingmodules for reporting information. Further example modules includesensor operation modules configured to operate sensing element(s) todetect input, identification modules configured to identify gesturessuch as mode changing gestures, and mode changing modules for changingoperation modes. In one embodiment, processing system 110 comprises amodule for controlled updating of the electronically-readableinstructions of processing system 110.

In some embodiments, the processing system 110 responds to user input(or lack of user input) in the sensing region 120 directly by causingone or more actions. Example actions include changing operation modes,as well as GUI actions such as cursor movement, selection, menunavigation, and other functions. In some embodiments, the processingsystem 110 provides information about the input (or lack of input) tosome part of the electronic system 150 (e.g., to a central processingsystem of the electronic system that is separate from the processingsystem 110, if such a separate central processing system exists). Insome embodiments, some part of the electronic system 150 processesinformation received from the processing system 110 to act on userinput, such as to facilitate a full range of actions, including modechanging actions and GUI actions. In one embodiment the processingsystem may be configured to operate in a low-power mode with a reducedmeasurement rate and/or a report rate. In various embodiments, thelow-power mode may include, but is not limited to, reduced transmitterscan rate, reduced frame rate, reduced backlight power, simultaneouslydriving multiple transmitters with a similar transmitter signal, etc.

For example, in some embodiments, the processing system 110 operates thesensing element(s) of the input device 100 to produce electrical signalsindicative of input (or lack of input) in the sensing region 120. Theprocessing system 110 may perform any appropriate amount of processingon the electrical signals in producing the information provided to theelectronic system 150. For example, the processing system 110 maydigitize analog electrical signals obtained from the sensor electrodes.As another example, the processing system 110 may perform filtering orother signal conditioning. As yet another example, the processing system110 may subtract or otherwise account for a baseline, such that theinformation reflects a difference between the electrical signals and thebaseline. As yet further examples, the processing system 110 maydetermine positional information, recognize inputs as commands,recognize handwriting, and the like.

“Positional information” as used herein broadly encompasses absoluteposition, relative position, velocity, acceleration, and other types ofspatial information. Exemplary “zero-dimensional” positional informationincludes near/far or contact/no contact information. Exemplary“one-dimensional” positional information includes positions along anaxis. Exemplary “two-dimensional” positional information includesmotions in a plane. Exemplary “three-dimensional” positional informationincludes instantaneous or average velocities in space. Further examplesinclude other representations of spatial information. Historical dataregarding one or more types of positional information may also bedetermined and/or stored, including, for example, historical data thattracks position, motion, or instantaneous velocity over time.

In some embodiments, the input device 100 is implemented with additionalinput components that are operated by the processing system 110 or bysome other processing system. These additional input components mayprovide redundant functionality for input in the sensing region 120, orsome other functionality. FIG. 1A shows buttons 130 near the sensingregion 120 that can be used to facilitate selection of items using theinput device 100. Other types of additional input components includesliders, balls, wheels, switches, optical proximity sensor, and thelike. In some embodiment, the use of additional input components mayalso be facilitated by indicating frame function on a display or byrejecting accidental user input using positional information from theinput device. Conversely, in some embodiments, the input device 100 maybe implemented with no other input components.

In some embodiments, the input device 100 comprises a touch screeninterface, and the sensing region 120 overlaps at least part of anactive area of a display screen. For example, the input device 100 maycomprise substantially transparent sensor electrodes overlaying thedisplay screen and provide a touch screen interface for the associatedelectronic system 150. The display screen may be any type of dynamicdisplay capable of displaying a visual interface to a user, and mayinclude any type of light emitting diode (LED), organic LED (OLED),cathode ray tube (CRT), liquid crystal display (LCD), plasma,electroluminescence (EL), or other display technology. In oneembodiment, the display may include dot inversion, line inversion, frameinversion, or other methods. In various embodiments, the display maycomprise a DC Vcom signal or an AC Vcom signal. In further embodiments,the display may comprise patterned vertical alignment, in planeswitching, plan to line switching or other wide viewing angleimprovements. The input device 100 and the display screen may sharephysical elements. For example, some embodiments may utilize some of thesame electrical components for displaying and sensing. As anotherexample, the display screen may be operated in part or in total by theprocessing system 110. In various embodiments, a complete pixel updateto the display device may be referred to as a display frame. A displayframes may be updated progressively (e.g., updating each display pixelrow on a one-by-one basis) or interlaced (e.g., during a first period afirst half of the display is updated and during a second period a secondhalf of the display is updated. In various embodiments, the portion ofthe display update time used for capacitive sensing may be limited bythe settling time of the combination electrodes, by the signal to noiseratio or interference. In one embodiment, this time may be based on thesettling time and any tolerance. The settling time can be modeled as anRC time constant. Reducing either variable of a combination electrodemay reduce the settling time. Further, reducing the tolerance may alsoreduce the settling time. In various embodiments by disposing theelectrodes on different layers, using thicker layers, wider or narrowerelectrodes or different connection methods (e.g., multiple connection oradditional high conductivity jumpers) the RC time constant may bereduced.

It should be understood that while many embodiments of the invention aredescribe (in the context of a fully functioning apparatus, themechanisms of the present invention are capable of being distributed asa program product (e.g., software) in a variety of forms. For example,the mechanisms of the present invention may be implemented anddistributed as a software program on information bearing media that arereadable by electronic processors (e.g., non-transitorycomputer-readable and/or recordable/writable information bearing mediareadable by the processing system 110). Additionally, the embodiments ofthe present invention apply equally regardless of the particular type ofmedium used to carry out the distribution. Examples of non-transitory,electronically readable media include various discs, memory sticks,memory cards, memory modules, and the like, Electronically readablemedia may be based on flash, optical, magnetic, holographic, or anyother storage technology.

Some embodiments utilize a construction of two-layer indium tin oxide(ITO) polyethylene terephthalate (PET). The dimensions such as width andthickness of PET, ITO sensor, and other materials (which may includepolarizing elements as part of an LCD) may be sized to improve signal tonoise and to reduce interference. A sensor pattern in sensing region 120may include, among other electrode configurations, substantiallystraight electrodes, patterned electrodes, and/or two-pronged (or more)receiver electrodes over thick, bar-shaped transmitter electrodes. Inother embodiments, the transmitter electrodes may be patterned. Theexternal traces may be routed to a PCB (printed circuit board)surrounding the sensor pattern. Other embodiments include single-layerITO on glass with or without and additional ground or guard layer forshielding purposes. Conductors other than ITO, such as metal, can alsobe used. In various embodiments, the conductors may include silvernano-wires, organic conductors PEDOT (Poly (3,4-ethylenedioxythiophene))or carbon-nano-rubes). A face sheet or a “window” lens (without or withan air gap) may be placed over the sensor electrodes. In one embodiment,the receiver electrodes may be disposed on the lens of a display or onthe color filter substrate (color filter glass) of a display.

FIG. 1B shows a portion of an example sensor electrode pattern which maybe disposed to generate all or part of the sensing region of an inputdevice, according to an embodiment. For purposes of clarity ofillustration and description, a simple rectangular pattern isillustrated. The sensing pattern is made up of a plurality of receiverelectrodes 170 (170-1, 170-2, 170-3, . . . 170-n) and a plurality oftransmitter electrodes 160 (160-1, 160-2, 160-3, . . . 160-n) Whichoverlay one another and are disposed on a substrate 180. In otherembodiments, the plurality of receiver electrodes 170 (170-1, 170-2,170-3, . . . , 170-n) and plurality of transmitter electrodes 160(160-1, 160-2, 160-3, . . . 160-n) which overlay one another and aredisposed on a multiple (or bonded) substrates. Touch sensing pixels arecentered at locations where transmitter and receiver electrodes cross.In some embodiments, the receiver electrodes may be patterned to reducevisibility. In some embodiments, electrically floating electrodes may bepatterned between receiver electrodes or portions of receiver electrodesto reduce visual performance. In some embodiments, the transmitterelectrodes are combination electrodes and are patterned to providedisplay functionality. In various embodiments, touch sensing includessensing input objects anywhere in sensing region 120 that may compriseno contact with any surfaces of input device 100, contact with an inputsurface (e.g., a touch surface) of input device 100, contact with aninput surface of input device 100 coupled with some amount of appliedforce or pressure, and/or a combination thereof.

It is appreciated that some form of insulating material is typicallydisposed between transmitter electrodes 160 and receiver electrodes 170.In some embodiments, transmitter and receiver electrodes may be disposedon the opposite sides of substrate 180 or even on separate substrateswhich are stacked proximate one another. In some embodiments describedherein, substrate assembly 180 is a substrate disposed in a display of adisplay device. For example, substrate assembly 180 may be a substrateused in the stack up of a liquid crystal display (LCD). In oneembodiment, transmitter electrodes 160 and receiver electrodes 170 maybe disposed on a similar layer of substrate assembly 180, where thetransmitter electrode comprise a plurality of jumpers disposed on asecond layer of the substrate assembly 180. In another embodiment, thetransmitter electrodes 160 are disposed on a first layer of a substrateassembly 180 and the receiver electrodes 170 on a second layer of thesubstrate assembly 180 and jumpers are not required. In someembodiments, the transmitter electrodes 160 and receiver electrodes 170may be disposed on a color filter substrate layer of a display. Inanother embodiment, receiver electrodes 170 may be disposed on a colorfilter substrate layer and the transmitter electrodes 160 may bedisposed on a TFT (Thin Film Transistor) substrate layer of a display.In another embodiment, the receiver electrodes may be disposed on aprotective layer, polarizer layer, lens glass or any other layer of adisplay device. In yet further embodiments, the receiver electrodes maybe disposed on any layer above the transmitter electrodes.

Processing system 110 may detect changes in capacitive coupling betweentransmitter electrodes and receiver electrodes when an input object suchas a human digit or a stylus is brought near. When the sensor comprisesmultiple transmitter electrodes (e.g., transmitter electrodes 160) ormultiple receiver electrodes receiver electrodes 170), multiplecapacitive couplings are formed in a spatially distributed fashion. Aset of measurements of such multiple capacitive couplings is oftenreferred to as a capacitive “frame”, or a capacitive “image”. Such acapacitive “image” represents the magnitudes of the capacitive couplingsduring a particular period of time, Successive capacitive “images”represent the magnitudes or changes of the capacitive couplings duringsuccessive periods of time. In one embodiment, exciting transmitterelectrodes in sequence may be described as scanning the capacitivesensor device. Such successive images can be used to track the motionsof objects in time as they move throughout a sensing region. The rate atwhich successive images are captured is known as the capacitive sensorframe rate or report rate. In various embodiments, the capacitive framerate may be different than the display frame rate. The set ofmeasurements may comprise independently measuring the change in couplingof multiple “pixels” in a capacitive “image” associated with differentgroups of combination electrodes and/or different groups of receiverelectrodes. In one embodiment, a baseline capacitive “image” is used todetermine the change in capacitive coupling. Multiple capacitivebaseline “images” may be used. The selection of the baseline image maybe related to the relative phase of the display pixel rows relative thetransmitting group of combination electrodes. Multiple baselines may bestored in various formats, including compressed and uncompressedformats. Compressed formats may include differences between baselines,or scaled, filtered and encoded versions of baselines. In oneembodiment, more than one capacitive “image” may be collected from asingle display frame. In various embodiments, the transmitter electrodesand combination electrodes may be driven with a substantiallyindependent coding scheme such that a capacitive image can be determinedfrom the independently driven transmitter groups.

In some display device embodiments, transmitter electrodes 160 areshared between a capacitive sensor device and a display device. In oneembodiment of an integrated capacitive sensor device and display device,transmitter electrodes 160 act as transmitters for the capacitive sensordevice and also as common electrodes (drivers) for display update of adisplay in a display device. In such embodiments of an integratedcapacitive sensor device and display device, each transmitter electrode160 (e.g., 160-1) can be referred to as a “combination electrode”. Invarious embodiments, each common electrode is a segment or multiplesegments of a segmented Vcom electrode. In some embodiments, thesegments of a segmented Vcom electrode may be referred to as thespatially related display pixel rows or display rows of the display. Inone embodiment, a fraction of the display area may be capacitivelymeasured. In another embodiment, this occurs during a non-display updatetime of the display. In yet another embodiment, the entire display areacan be measured or scanned during a single contiguous non-display updatetime of sufficient length. In various embodiments, the entire displaymay be measured during a single display frame. In other embodiments, thecapacitive sensor may have faster report rates associated with updatingonly a fraction of the display area.

In many embodiments where combination electrodes 160 are utilized, oneor more other components may also be integrated and shared between thecapacitive sensing functions and the display functions. For example,processing system 110 may also be shared within an integrated capacitivesensor device and display device to coordinate and/or control some orall aspects of the capacitive sensing functions and the displayfunctions. Though not illustrated, in one embodiment, other displaypixel row electrodes can be layered in between or on top of transmitterelectrodes 160 and receiver electrodes 170. Display device 600 of FIG.6, shows one example of display pixel rows. In various embodiments, adisplay is updated by selecting a row of pixels to be updated anddriving a voltage (or controlling a current) on the selected pixelsthrough individually controlled source drivers to a common electrodeassociated to that row covering an array of pixels or sub pixels). Inone embodiment, the common electrode associated with multiple displaypixel rows may be combined into a single combination electrode wheresubstantially the same voltage for that combination electrode is appliedto each display pixel row by processing system 110 for both displayupdate and capacitive sensing.

Turning now to FIG. 1C, FIG. 1C shows different phases groups (or sets)of non-overlapping combination electrodes 160-4-160-7. As can be seen inFIG. 1C, groups of combination electrodes 160-4-160-7 comprise differentsegments of a segmented Vcom electrode (or display pixel rows).

FIG. 1D shows different phases overlapping groups of combinationelectrodes 160-8-160-11. As can be seen in FIG. 1D, each group ofcombination electrodes shares at least one segment of a segmented Vcomelectrode (or display pixel rows) with another group of combinationelectrodes. While 160-4 through 160-11 are referred to groups ofcombination electrodes, in other embodiments, they may be referred to ascombination electrodes or groups of segments of a segmented Vcom. Invarious embodiments, each group of combination electrodes may driven atdifferent times or at least two of the combination electrodes may bedriven at the same time in order to scan the frame or a portion thereof.Further, the common electrodes may be disposed on the TFT glass in somedisplays (e.g., In Plan Switching (IPS) or Plan to Line Switching (PLS))or on the bottom of the color filter glass of some displays (e.g.,Patterned Vertical Alignment (PVA) or Multi-domain Vertical Alignment(MVA)).

In some embodiments, processing system 110 may be configured to transmitwith more than one group of combination electrodes at different times(e.g., transmitting with one group of combination electrodes while asecond group of combination electrodes are driven with a stationaryvoltage) during a non-display update time associated with updating aframe of a display (e.g., vertical blanking time).

Turning now to FIG. 1E, FIG. 1F shows input device 195 comprisingcombination electrodes 161, receiver electrodes 170, processing system110-1, processing system 110-2 and synchronization mechanism 191.Processing system 110-1 is coupled with receiver electrodes 160 andconfigured to receive resulting signals with receiver electrodes 161. Inother embodiments processing system 110-1 is coupled with portion of orall of combination electrodes 161. In one further embodiment, inputdevice 195 comprises transmitter electrodes and processing system 110-1is coupled with the transmitter electrodes. Processing system 110-2 iscoupled with combination electrodes 161. In one embodiment processingsystem 110-2 comprises display control circuitry for controlling thedisplay of images. The display control circuitry is configured to applyone or more pixel voltage(s) to the display pixel electrodes throughpixel source drivers (not shown). The display control circuitry may bealso configured to apply one or more common drive voltage(s) to a commonelectrode. In one embodiment, the common drive voltage may or may notinvert in synchronization with a drive cycle of the image displaycontrol (e.g. line inversion). In one embodiment, the combinationelectrodes may also be combination source drivers and capacitive sensortransmitters. In some embodiments, receiver electrodes may also sharefunctionality with source driver electrodes. In one embodiment,processing system 110 comprises processing system 110-1 and processingsystem 110-2. In another embodiment, processing system 110-1 andprocessing system 110-2 may be implemented as integrated circuitry andmodules of a single processing system.

Processing system 110-1 may be configured to control capacitive sensingand processing system 110-2 may be configured to control displayupdating. Processing system 110-1 may be coupled with processing system110-2 via synchronization mechanism 191. Processing system 110-1 andprocessing system 110-2 may communicate with each other viasynchronization mechanism 191. In one embodiment, processing system110-2 may change the set of combination electrodes modulated to scan thesensing area in response to a synchronization signal. In one embodiment,processing system 110-1 may provide a signal synchronized with samplingthe receivers to processing system 110-2 via synchronization mechanism191. In another embodiment, processing system 110-2 may shift thetransmitter signal (display reference voltage) to another transmittersignal compatible for driving the combination electrodes. In oneembodiment, the display reference voltage may be provided to processingsystem 110-1 via synchronization mechanism and processing system 110-1may use the reference voltage as the transmitter signal to be driven onthe combination electrodes. In other embodiment, the synchronizationmechanism 191 may share reference signals between processing system110-1 and processing system 110-2. Synchronization signals may be sharedbetween processing system 110-1 and processing system 110-2 to generatedisplay compatible timing for the combination electrodes. In oneembodiment, synchronization signals that may indicate pixel row timingand vertical frame timing may be shared and used for synchronization Inother embodiments, synchronization signals can also be used for otherpurposes within either processing system 110-1 or 110-2, such as, todirectly drive different transmitter electrodes or receive withdifferent receiver electrodes or to initialize input elements (e.g.,buttons, scroll strips, etc.). In some embodiments, where processingsystem 110 comprises processing system 110-1 and processing system110-2, the synchronization mechanism may be comprised by processingsystem 110 and generate display compatible timing for the combinationelectrodes. In various embodiments, the Vcom of the display is a displayreference common voltage. In such embodiments, the reference voltage maybe shared between processing system 110-1 and processing system 110-2 toprovide display compatible synchronization voltages for the combinationelectrodes. In one embodiment, display compatible synchronizationvoltages comprises transmitter signals provided for capacitive sensingthat do not interfere with display operation by a significant amount. Inone embodiment, the displayed image does not comprise significantvisible display defects. In another embodiment, the display compatiblesynchronization voltages comprise pixel update voltages that during thepixel update time do not interfere with capacitive sensing. In someembodiment, this comprises not causing significant report positionerrors for the capacitive sensor system.

In various embodiment, to avoid interference between display updates andcapacitive sensing processing system 110 may suspend generation anddriving of voltage transitions (e.g., edges) during the display updatetime. In another embodiment, processing system 110 may gate off thereceiver circuitry of processing system 110 or suspend demodulationduring “noisy” display update times. In other embodiments, to avoidinterference between display updates and capacitive sensing processingsystem 110-1 and/or processing system 110-2 my suspend generation anddriving of voltage transitions (e.g., edges) during the display updatetime. The display update time may be communicated to processing system110-1 from processing system 110-2 via synchronization mechanism 191. Inyet another embodiment, processing system 110-2 may signal processingsystem 110-1 to gate off the receiver circuitry of processing system110-1 or suspend demodulation during “noisy” display update times viathe synchronization mechanism 191.

Synchronization between separate display driving electronics processingsystem 110-2) and capacitive sensing electronics (e.g., processingsystem 110-1) may be achieved by communicating between systems withsynchronization mechanism 191 (e.g., an electrode carrying electronicpulses). In some embodiments, a triggering system may allow forsynchronization where processing system 110-1 and processing system110-2 have separate clock domains. The triggering system may havestandard triodes that are comparable to those that are available in anoscilloscope (e.g., delay time, active time, trigger hold off time etc.)or may use more generic playback techniques. In other embodiments,vector tables, LUTs (look up tables), and the like may be used ingenerating the trigger events and timing. In other embodiments, timingrecovery signals (e.g., delay locked loops, phase locked loops, orothers) can be used for synchronization may also be used. In yet otherembodiment, processing system 110-1 may also communicate synchronizationsignals for generating transitions on (e.g., modulating) combinationelectrodes, gating or selecting which electrodes are modulated (e.g.,selecting sets of combination electrodes). The synchronization signalsmay trigger events, or for space savings may drive more complex signals(e.g., shift register clocking for TFT glass). In some embodiments, aground reference voltage will be communicated between the processingsystems 110-1 and 110-2. In other embodiments, other voltages (e.g., acommon display voltage like Vcom, Vcom+, Vcom−, etc) relative to theground may also be communicated. Such a communicated reference may alloweither processing system to drive combination electrodes and reduce anydetrimental effects of capacitive sensing on display performance, or ofdisplay updates on capacitive sensing performance.

Coupling 190-1 shows that multiple combination electrodes may be coupledtogether and then coupled with processing system 110-2. In such aconfiguration, multiple combination electrodes may be drivensimultaneously with similar transmitter signals. Coupling 190-2 showsthat individual combination electrodes may be individually coupled withprocessing system 110-2. Coupling 190-3 shows that the coupling betweenindividual combination electrodes and processing system 110-2 comprisesswitches and when a switch is open the corresponding combinationelectrodes are not driven and when a switch is closed the correspondingcombination electrodes may be driven. In some embodiments, the switchesmay couple to various display voltages and their associated generatingelectronics, Coupling 190-4 shows that either end of combinationelectrodes may be coupled with processing system 110-2. In anotherembodiment, combination electrodes may be coupled at both ends withprocessing system 110-2 as shown by coupling 190-6 and 190-1. In anotherembodiment, combination electrodes may be coupled at both ends withprocessing system 110-1. Coupling 190-5 shows that combinationelectrodes may be coupled (e.g., driven by) with processing system110-1. In further embodiments, combination electrodes may be coupledwith both processing system 110-1 and processing system 110-2.

Section 1 Varying Demodulation to Avoid Interference

FIG. 2 shows an embodiment of a capacitive measuring system 200configured to demodulate and filter samples of a received resultingsignal to improve the interference susceptibility of a capacitivesensor. Throughout the following description, demodulate may refer toboth demodulating and filtering. Even though one example capacitivemeasuring system is shown, other known (e.g., discrete time andcontinuous time) capacitive measuring systems demodulators and filtersmay also be used. In one embodiment, charge is accumulated duringtransitions of the transmitter signal (e.g., as the transmitter signalis changed from High to Low, Low to High, or other similar voltages)where current is transferred through the sensed capacitance C andaccumulated into the charge accumulating capacitor C_(FB) which iscoupled between the inverting input and the output of integratingamplifier 210. A reference voltage Vref is coupled with thenon-inverting input of integrating amplifier 210. The voltage output onC_(FB) changes in response to the transferred charge. This voltageOutput on C_(FB) is integrated by amplifier 210. After some“integration” time, T_(int), an amount of charge is accumulated and asample is taken of the voltage output and demodulated. The integrationtime may be variable, but unless the time is substantially long comparedto any other sensor time constants, the accumulated charge may depend onT_(int), which is undesirable. In one embodiment, integration and resettimes may also be delayed for transmitter transitions where the sensordelays the charge transfer.

The voltage output of the accumulating capacitor may be reset for a“reset” time T_(reset), which can be variable, following integration. Inone embodiment, resetting is accomplished by removing accumulated chargefrom C_(FB) by closing switch T_(reset). This causes the output voltageto return to its “zero” state. Here, “zero” state is V_(ref), theequilibrium output value when no signal is being integrated. On asubsequent voltage transition of opposite polarity, charge can beaccumulated to develop another voltage which is sampled on the output ofC_(FB). Thus, in many embodiments, T_(SAMPLE)=T_(DEMOD)/2, or less,although this is not required. In other embodiments, continuous timedemodulation and filtering may also be used, or single transitionpolarity may be used per transmitter period.

A larger number of demodulations, of the same or varying weights, mayinclude over sampling, harmonic canceling, correlated double sampling orDC sensitive single polarity constant weighting. The two output voltagesamples can be filtered in demodulator 211 by combining them at thedemodulation frequency (or other variable timing) to obtain a measure ofthe capacitance. Other sensing methods may also be used without changingthe nature of the described embodiments. For example other waveformshapes (e.g., trapezoidal), capacitive current transfer measurements(e.g., current multiplication), or demodulation methods (e.g.,heterodyne detection) may be used in addition to those described herein.Also, other demodulation and resetting schemes are possible. In oneembodiment, the reset step may not be present (e.g., it may be of zerolength or continuous). As described below, it can be advantageous toallow the timing of the demodulation T_(DEMOD) and demodulationfrequency) to be different than the timing of the transmitter signal(e.g., T_(SIGNAL) and transmitter frequency) in order to facilitateinterference avoidance. It is also advantageous to allow transmitterfrequency to be different than the row update rate (or fractional rowupdate for a single color of a display device) of a display device inorder to facilitate interference avoidance. In one embodiment, thetransmitter frequency is a reciprocal of the period between transitionsand/or demodulated samples.

FIG. 3A illustrates a waveform 310A of a capacitive sensor using ademodulation frequency that is the same as the transmitted transmittersignal frequency. Each transition results in the update of a singledisplay pixel row. In various embodiments, it is possible to transmitwith multiple segmented Vcom electrode segments (e.g., sets ofcombination electrodes during each transition. A block (groups or sets)of transmitter electrodes can, therefore, be comprised of one or moreVcom electrode segment(s) corresponding to multiple display pixel rows.These display pixel rows need not be contiguous. In one embodiment,where a combination electrode is utilized, the frequency of thetransmitter signal for capacitive sensing and updating the displaydevice are the same, and thus the interference susceptibility spectrum(that is, the interference susceptibility versus frequency) maybe fixed.In one embodiment, one or more transitions per display row may occur.The transitions may occur between row updates or between pixel orsub-pixel updates on a display row. In one embodiment, the transitionsoccur during the time the source drivers are multiplexed to multiplepixels or sub-pixels of a row. In another embodiment, the transitionsmay occur during a non-display update time after the display rowselection is updated when the display source drivers are substantiallyde-coupled.

An example of timing of the touch sensor demodulation operation relativeto the Vcom waveform 310A is illustrated in FIG. 3A. As indicated by key350 (which also applies to FIGS. 3B, 3C, and 3D), the demodulatorsamples are marked by X's, X's within a circle, or empty circles; thesignal 310 is denoted by the line of the square wave; horizontal arrowsdenote the length of an integration interval Tint; and vertical arrowsdenote demodulation polarity. In one embodiment, the filtering of thedemodulated samples may be uniformly weighted. In one embodiment,intermediate samples may be ignored (e.g., filtered weighted with zeroamplitude).

In FIGS. 3A-3D, X's without a circle indicate demodulation samples whichoccur after an integration period following a voltage transition. Thesedemodulation samples contain new information and are referred to as“signal samples”, The X's within a circle, on the other hand, occurwithout integration of a voltage transition. These demodulation samplesare called “implicit samples” and may not contain any new signalinformation. Implicit samples may occur after a reset period but beforethe next voltage transition as shown in FIG. 3A. These implicit samplesmay or may not be independently filtered. In one embodiment, theimplicit samples may be differentially filtered based on the differencebetween two signal samples and the distance between implicit samples.The implicit samples can be used to implement, for instance,double-correlated sampling. However, implicit samples may includeinterference information and are therefore important for filtering andaffecting the interference susceptibility spectrum. The label,“T_(SAMPLE)” is utilized to demarcate a time period during which a setof samples may be obtained and filtered (e.g., summed, low passedfiltered, etc). The label, “T_(CYCLE)” is utilized to demarcate theperiod of the transmitter signal frequency.

The demodulation signal samples may be generated by integrating thecoupled charge transfer caused by the voltage transition. In oneembodiment, the demodulation signal samples may be generated byintegrating between the implicit samples and the end of the signalintegration. In order not to disturb the display or have the displaydisturb the capacitive sensing, the voltage transition (or transitionswhen two or more are used) may be timed to occur during a non-displayupdate period associated with updating a display row. In one embodiment,sampling during the pixel update period is also avoided becauseinterference from the display, such as that caused by multiplexedRed-Green-Blue (RGB) image data, can be injected into the receiverelectrode during this time. In one embodiment, the location of themodulated combination electrodes may be correlated with the pixel lineselected for update. In one embodiment, the beginning of the integrationtime is delayed from the transmitter transition to accommodatepropagation delays. In one embodiment, the propagation delays are due toa display device switching time.

As shown in FIG. 3A, each row of the touch sensor may include one ormultiple voltage transitions which occur while the at least one displayline is updated. In one embodiment, the voltage transitions occur duringa non-display update period. In another embodiment, the voltagetransitions occur during a non-display update period and before the nextdisplay pixel row is updated. According to the embodiment of FIG. 3A,one transition would occur as one display row is updated before a newreceiver electrode (e.g., receiver electrode 1604) sampled. However, asmultiple display rows are updated while a single receiver electrode issampling, there will be multiple transitions filtered to comprise ademodulator output. In one embodiment, multiple combination electrodes(or sets or groups) may be driven with the same change in voltage duringthe non-display update time and driven to the same different voltage(e.g., a common voltage such as Vcom) during the display update time. Inother embodiments, as described in conjunction with FIG. 9, a waveformmay have multiple transitions that are timed to take place during anon-display update time associated with updating of a display pixel row(e.g., during the horizontal blanking period that occurs after a row isupdated). In another embodiment, the multiple transitions are timed totake place during the non-vertical blanking time of the display betweendisplay frames. After the at least one display pixel row or frame isupdated, a receiver electrode is sampled and demodulated before the nextdisplay line is updated. In various embodiments, multiple independentblocks of combination electrodes associated with spatially separateddisplay rows can be modulated at different times between display rowupdates or display frame updates to scan the sensing area. Themodulators may be demodulated and filtered substantially simultaneouslyby multiple receiver sensor electrodes 170 to compose a scannedcapacitive “image” or spatial array of capacitive measurements to trackmultiple input objects independently.

FIG. 3B illustrates an example waveform having a sensing demodulationfrequency that is different than the transmitter signal frequency toimprove interference susceptibility. In one embodiment, to improve theinterference susceptibility, a demodulation frequency that is differentthan the transmitter signal frequency is used. In One embodiment, thisis enabled by including additional implicit samples in the demodulation.The time indicated by T_(repeat) FIGS. 3A, 3B and 3C is the samplingtime of FIG. 3A and also the time between the sets of repeated samplesof FIGS. 3B and 3C.

In FIG. 3B the demodulation frequency is changed by increasing thenumber of samples occurring during the sample timing (e.g., from twosamples for T_(SAMPLE) to four samples for T_(SAMPLE1)). Note that it isalso possible to decrease the number of samples by not sampling duringevery transmitter signal transition. Also the number of samples perT_(SAMPLE1) can be changed from one cycle to the next. The phase ofsubsequent cycles can also be modulated from one cycle (T_(CYCLE)) tothe next. In one embodiment, the weighting of the samples may be changedin subsequent samples to avoid interference by differently demodulatingthe signal.

FIG. 3C illustrates another example waveform having a demodulationfrequency that is different than the frequency of the transmittedtransmitter signal. The sample time between demodulated samples of FIG.3C (as shown by samples taken in T_(sample2)) is shorter than that ofthe FIG. 3B (as shown by samples taken during T_(sample1)); therefore,the demodulation frequency of FIG. 3C is higher than that of FIG. 3B,even though the repeat time (T_(REPEAT)) is the same.

By varying the demodulation frequency it is possible to cancel differentharmonics within the interference spectrum. The method by which multipledemodulation cycles can occur during one VCOM transition one horizontaldisplay row) period is explained below. Further, the integration(T_(int) in FIG. 3A), reset time and sampling rate can be adjusted tomodulate in phase, amplitude and frequency, thus causing theinterference susceptibility spectrum to be changed. For example, thedemodulation sign can be changed and the relative phase of thetransmitter signal, T_(RESET) and T_(int) can be changed. Also, themodulations of frequency or phase in the demodulation may be used tospread the interference susceptibility spectrum, allowing for increasedinterference tolerance. In one embodiment, the weighting of the samplescan be changed (i.e., increased, decreased or changed in sign) toincrease interference tolerance. The results of the demodulations mayalso be filtered using, for example but not limited to Infinite ImpulseResponse (IIR) filters and Finite Impulse Response (FIR) filters,continuous time filters and band pass filters. In other embodiments, asecond demodulator may also be used after filtering. In someembodiments, the interference susceptibility of an input device can bealtered by demodulating a received resulting signal with more than oneof the above described methods.

In one embodiment, interference avoidance can be achieved by varying thesensor demodulation frequency and by sampling the received signal morethan once (even for transmitter signals having only one transition) foreach half-cycle of the transmitter signal, which allows many more typesof demodulations and frequencies to be used. Consider an example where apair of signal samples may have a demodulation frequency of 250 kHz (2μs separation for each demodulation polarity), but voltage transitionsmay only occur at 50 kHz (each edge of the 25 kHz transmitter signalfrequency). This provides one positive and one negative signal samplefor four demodulation samples (there will be two signal samples and twoimplicit samples) each signal sample pair spaced apart by 20 μs in the40 μs of the full transmitter modulation cycle. In some embodiments, thesum of samples containing the transitions signals are filtered the samethe response to the capacitive signal will remain the same, independentof the weighting of other samples.

In some embodiments, as illustrated in FIG. 3D, there may be zero signal(intermediate samples) that are taken between positive and negativedemodulated signal samples. In the embodiment which is illustrated byFIG. 3D, there are seven intermediate samples between positive andnegative demodulated signal samples. Intermediate samples can befractional cycles of the demodulator frequency which may or may not beused during processing. Adding in these intermediate signals alters theinterference susceptibility of the input device, but not necessarily thesignal response. For example, in one embodiment, adding in theintermediate samples create 50 kHz susceptibility sidebands off of a 250kHz resulting signal (with an envelope set by the integration time) thatgo to 0 at DC due to the short integration time. The interferencesusceptibility spectra for the single pair demodulation scheme and thedouble demodulation scheme (or higher order sine, shaped or FIRdemodulation loop) with the same resulting signal are substantiallyorthogonal (e.g., non-substantially overlapping peaks) include: a firstspectrum with peaks at (1+2N)×25 kHz; and a second spectrum with peaksat N×50 kHz. The ability to select between these two demodulationschemes therefore enables effective interference avoidance viademodulation frequency shifting even when the frequency of thetransmitted transmitter signal is substantially fixed. In variousembodiments, when the demodulating frequency is different than thetransmitter signal frequency, the demodulated result is not at asubstantially stationary voltage and it can be selectively filtered ordemodulated and filtered again. Further, in various embodiments, thedemodulation frequency changes relative to the transmitter signalfrequency. In other embodiments the filter can be changed to filter forthe frequency difference between the demodulation frequency andtransmitter signal frequency.

In further embodiments, multiple higher rate samples may be taken aroundeach transition of the resulting signal, allowing for modulation of boththe phase and frequency of the received resulting signal. For example,in one embodiment, some number of samples, labeled as intermediatesamples in FIG. 3D, may be included in the signal calculation to changethe frequency susceptibility. The samples may be taken in an analog form(e.g., sampled onto a capacitor) or in a digital form (e.g., sampledwith an analog-to-digital converter (ADC)).

It is appreciated that changing demodulation schemes can be accomplishedwhen it is noted that the interference is above some predetermined levelwhen using one scheme. When this happens an alternative demodulationscheme can then be employed. In some embodiments, one or moredemodulation schemes may be deployed and the one with the leastinterference may be selected and used. This will be described in moredetail within the following paragraphs.

First Example Processing System

FIG. 4 illustrates a first example processing system 110A which may beutilized with an input device (e.g., input device 100), according tovarious embodiments. Processing system 110A may be implemented with oneor more ASICs, one or more ICs, one or more controllers, or somecombination thereof. In one embodiment, processing system 110A iscommunicatively coupled with a plurality of transmitter electrodes (orcombination electrodes) and plurality of receiver electrodes thatimplement a sensing region 120 of an input device 100. In one embodimentof input device 100, processing system 110A includes transmittercircuitry 405, receiver circuitry 415, demodulation circuitry 425, anddemodulation type selector 435. Some embodiments additionally includecomputation circuitry 445.

Transmitter circuitry 405 operates to transmit transmitter signals withone or more transmitter electrodes (or combination electrodes) that aredisposed in a sensing region. In a given time interval, transmittercircuitry 405 may transmit a transmitter signal (waveform) with one ormore of a plurality of transmitter electrodes. Transmitter circuitry 405may also be utilized to couple one or more transmitter electrodes of aplurality of transmitter electrodes to ground or to a constant voltagesuch as a reference voltage (e.g., Vcom or some other reference voltage)when not transmitting with such transmitter electrodes. Transmittercircuitry may scan through different transmitter (combination)electrodes at different time to scan through the sensing region. Thetransmitter signal may be a square wave, trapezoidal wave, or some otherwaveform. In various embodiments, waveforms 910, 920, and 930 of FIG. 9illustrate some examples of waveforms which may be driven by transmittercircuitry 405 and transmitted with transmitter electrodes/combinationelectrodes. It should be noted, and will be further explained below,that waveforms 910, 920 and 930 illustrate that multiple transitions(e.g., two or more) can be made in the waveform of the transmittedtransmitter signal and timed such that the transitions occur during anon-display update time period horizontal blanking period or verticalblanking period). During the non-display update time, the transitionswill not have any effect upon display updating, but will provide extratransitions to sample for touch sensing. In another embodiment, thetransitions may be synchronous with the display update period (e.g., atsubstantially the same time as a pixel update in a row or display frameupdate).

Receiver circuitry 415 operates to receive resulting signals, viareceiver electrodes, which correspond to one or more transmittedtransmitter signals. The received resulting signals correspond to andmay include some version of the transmitter signal(s) transmitted viathe transmitter electrodes (e.g., the coupled charge). These transmittedtransmitter signals however, may be altered, changed or filtered in theresulting signal due to stray capacitance, interference (noise), and/orcircuit imperfections among other factors, and thus may differ slightlyor greatly from their transmitted versions. Resulting signals may bereceived, on one or a plurality of receiver electrodes during a timeinterval. In one embodiment, resulting signals may be received while notransmitter signal is transmitted with the transmitter electrode. Insuch embodiment, the resulting signals can be used to determine anamount of ambient/environmental interference. FIGS. 3A-3D illustratesampling of resulting signals which are received by receiver circuitry415 (e.g., after current is integrated to measure the coupled charge).In one embodiment, filtering the resulting signals at different phasesof the transmitter scan may be used for the measurement of capacitivechanges at different portions of the capacitive sensing area.

Demodulation circuitry 425 operates to demodulate the received resultingsignals. In various embodiments, demodulation circuitry comprises ademodulator and a filter. Demodulation circuitry 425 may be configuredto demodulate resulting signals in a plurality of different ways. In oneembodiment the resulting signal is affected by user input. For example,the received resulting signal may be affected in amplitude, phase orfrequency by a user input. This allows demodulation circuitry 425 toacquire a first demodulated output by demodulating a resulting signal ina first way, a second demodulated output by demodulating the resultingsignal in a second and different way from the first way that theresulting signal was demodulated, and so forth. In various embodiment,the first and second ways of demodulation differ because: demodulationcircuitry 425 weights samples differently in the first way as comparedto the second way; demodulation circuitry 425 takes samples that are ina different phase in the first way as compared to the second way;demodulation circuitry 425 utilizes different numbers of samples in thefirst way as compared to the second way; and/or there are differing timespans between the samples used by demodulation circuitry 425 in thefirst way as compared to the second way. Examples of different ways todemodulate the resulting signal are illustrated in FIGS. 3A-3D. Further,in other embodiments the demodulation circuitry 425 may furtherconfigured to demodulate the first resulting signal in a third way, thethird way different than the first and second ways. In furtherembodiments, the demodulation circuitry 425 may further be configured todemodulate the first resulting signal in any number of ways, where eachway is different. In a continuous time demodulator the demodulation mayvary in amplitude, frequency or phase. Further, in various embodiments,the post filtering of the demodulated signal may vary in bandwidth,cut-off frequency(s) or phase. In various embodiments, the postfiltering may include a second demodulation before sampling.

Demodulation type selector 435 operates to shift processing system 110Afrom using the first demodulated output for determining positionalinformation to using the second demodulated output for determiningpositional information. A variety of factors may be used to determinewhen to make such a shift. In one embodiment, demodulation type selector435 bases such a shift at least in part upon an amount of interference.The shift can be based on the amount of interference in the firstdemodulated output (for example, exceeding or not exceeding a presetamount of interference). The shift can be also be based on comparing anamount of interference in the first demodulated output to an amount ofinterference in the second demodulated output and utilizing thedemodulated output with the lowest amount of interference. In otherembodiments, the shift may also be based on stability or consistency ofthe measured interference. In some embodiments, similar comparisons andshifting can be made among more than two different types of demodulatedoutputs. In one embodiment, the amount of interference is a measure ofambient/environmental interference during a time when no transmittersignals are being driven by transmitter circuitry 405 or transmittedwith a transmitter electrode or combination electrode. In anotherembodiment, the amount of interference is a measure ofambient/environmental interference during a time when no transmittersignals are being driven by transmitter circuitry 405 or transmittedwith a transmitter electrode or combination electrode within thereceiver demodulation and filter band. In another embodiment, the amountof interference is a measure of the change in signal power during a timewhen it is determined that there is not a user input signal (e.g., thereis negligible coupling to any input object). For example, demodulationtype selector 435 can direct receiver circuitry 415 to receive a secondresulting signal during a time period when no transmitter signal istransmitted with any transmitter electrode by transmitter circuitry 405.Demodulation type selector 435 then directs demodulation circuitry 425to acquire a third demodulated output by demodulating this secondresulting signal in one of the first and second ways. Demodulation typeselector 435 determines an amount of interference that exists in thisthird demodulated output (and may also determine frequencies at whichambient interference exist) and can use this amount in selecting a typeof demodulation to use. In other embodiments, the demodulation typeselector 435 can further direct demodulation circuitry 425 to acquirethe third demodulation output and a fourth demodulation output bydemodulating the second resulting signal in both the first and secondways. In further embodiments, the demodulation type selector 435 canfurther direct demodulation circuitry 425 to acquire any number ofdemodulation outputs by demodulating the second resulting signal in aplurality of different ways. The demodulator type selector 435 can beconfigured to select the type of demodulation by comparing theinterference in each demodulation output to each other and selecting thetype of demodulation having the lowest amount of interference. In otherembodiments, the demodulation type selector 435 is configured to comparethe amount of interference in each demodulation output to apredetermined amount and select a type of demodulation that is below thepredetermined amount. Note, that in various embodiments, transmittercircuitry 405 may also change the modulation of the transmitterelectrodes (combination electrodes) to optimize the effectiveness of thedemodulator.

In one embodiment, when included, computation circuitry 445 operates todetermine a measurement of a change in transcapacitive coupling betweena transmitter electrode and a receiver electrode. Computation circuitrythen uses this measurement of change in transcapacitive coupling todetermine the position of an input object (if any) with respect tosensing region 120. The measurement of change is determined based on thedemodulated output that is acquired by demodulation circuitry 425. Inone embodiment, the first demodulated output is used when an amount ofinterference does not exceed a predetermined amount. In one embodiment,the second demodulated output is used when interference does exceed apredetermined amount. The selection of which demodulated output to use,is made, in some embodiments, by demodulation type selector 435 in themanner previously described. In one embodiment one or more filtered orcompressed baselines may be used to determine a change in capacitivecoupling.

In some embodiments, processing system 110A and the input device 100 ofwhich it is a part may be disposed in or communicatively coupled with anelectronic system 150, such as a display device. In one such integratedembodiment, transmitter electrodes are utilized as combinationelectrodes to support both display updating functions and touch sensingfunctions (e.g., for a touch screen device that is integrated with thedisplay of the display device). Thus, the transmitter signals driven onthese combination electrodes by transmitter circuitry 405 serve thepurpose of both display updating and touch sensing.

Example Method of Interference Avoidance for a Capacitive Sensor Device

FIGS. 5A and 5B illustrate a flow diagram 500 of an example method ofinterference avoidance for a capacitive sensor device, according tovarious embodiments. For purposes of illustration, reference will bemade to components of processing system 110A of FIG. 4 in thedescription of flow diagram 500. In some embodiments, not all of theprocedures described in flow diagram 500 are implemented. In someembodiments, other procedures in addition to those described may beimplemented. In some embodiments, procedures described in flow diagram500 may be implemented in a different order than illustrated and/ordescribed.

At 510 of flow diagram 500, in one embodiment, a transmitter signal istransmitted with a transmitter electrode of a capacitive sensor device.In one embodiment, transmitter circuitry 405 drives the transmittersignal. The transmitter signal is a waveform, such as a square wave,trapezoidal wave, or other waveform. In some embodiments, when acapacitive sensor device is utilized in conjunction with and/orintegrated with a display of a display device, the transmitter signal istransmitted and timed such that it includes two or more transitions thatoccur during a non-display update time period associated with updating arow of a display device. In some embodiments, processing system 110 maybe configured to transmit with more than one group of combinationelectrodes at different times or phases (e.g., transmitting with onegroup of combination electrodes while a second group of combinationelectrodes are driven with a stationary voltage) during a non-displayupdate time associated with updating a frame of a display (e.g.,vertical blanking time). In one such embodiment, the display device oneor more display rows thereof) at least partially overlaps a sensingregion of the capacitive sensor device.

At 520 of flow diagram 500, in one embodiment, a resulting signal isreceived with a receiver electrode of the capacitive sensor device. Aspreviously described, the resulting signal corresponds to thetransmitter signal. In one embodiment, the resulting signal is receivedfrom a receive sensor electrode by receiver circuitry 415.

At 530 of flow diagram 500, in one embodiment, a first demodulatedoutput is acquired by demodulating the resulting signal in a first way.In one embodiment, demodulation circuitry 425 acquires this firstdemodulated output by demodulating the resulting signal in a first wayof a plurality of different ways that it is capable of demodulating.

At 540 of flow diagram 500, in one embodiment, a second demodulatedoutput is acquired by demodulating the resulting signal in a second way,where the second way and the first way differ from one another. In oneembodiment, demodulation circuitry 425 acquires this second demodulatedoutput by demodulating the resulting signal in a second way of aplurality of different ways that it is capable of demodulating. It isappreciated that the first and second way of demodulation may bedifferent because samples are weighted differently in the second waythan the first way; because samples are sampled in a different phase inthe second way than in the first way; because a different number ofsamples is used in the second way than in the first way; and/or becausethe second way utilizes one or more different time spans between samplesthan the first way.

At 550 of flow diagram 500, in one embodiment, the method shifts fromusing the first demodulated output for determining positionalinformation to using the second demodulated output for determiningpositional information. The shift is based, at least in part, upon anamount of interference. In one embodiment, demodulation type selector435 determines when and to what type of demodulation to shift. In oneembodiment, the amount of interference is based on a measurement ofinterference in first demodulated output. In one embodiment, the amountof interference is based on a measurement of interference in the seconddemodulated output. Amounts can be compared to one another or to apredetermined scale. In one embodiment, the amount of interference is ameasure of ambient/environmental interference during a time when notransmitter signals are being transmitted by transmitter circuitry 405.For example, receiver circuitry 415 receives a second resulting signalfrom a receiver electrode during a time period when no in bandtransmitter signal is transmitted with any transmitterelectrode/combination electrode by transmitter circuitry 405. Forexample, in one embodiment, the demodulation and transmitted transmittersignals may be out of phase substantially orthogonal) such that theresulting signal is substantially zero. In one embodiment, this may beequivalent to not transmitting a transmitter signal with the transmitterelectrodes while receiving with the receiver electrodes. In oneembodiment, the effect of a user input signal can be distinguished frominterference which may be present independent of the transmittedtransmitter signal. In one embodiment, demodulation circuitry 425acquires a third demodulated output by demodulating this secondresulting signal in one of the first and second ways and determining anamount of interference that exists in this third demodulated output.This amount of interference from the third demodulated output is thenused as a basis for selecting among the plurality of different types ofdemodulation (e.g., first type, second type, etc.) to use.

At 560 of flow diagram 500, in one embodiment, the method furtherincludes a procedure of determining a measurement of a change intranscapacitive coupling between the transmitter electrode and thereceiver electrode based on the first demodulated output when the amountof interference is less than a first amount. In one embodiment, thiscomprises demodulation type selector 435 selecting a type ofdemodulation which will be employed by processing system 110A when theamount of interference is less than a first predetermined amount.Computation circuitry 445 then determines the measurement of a change intranscapacitive coupling (if any).

At 570 of flow diagram 500, in one embodiment, the measurement of changein transcapacitive coupling determined at 560 of flow diagram 500 isthen used by computation circuitry 445 in determining positionalinformation of an input object (if any) relative to sensing region 120.

At 580 of flow diagram 500, in one embodiment, the method furtherincludes a procedure of determining a measurement of a change intranscapacitive coupling between the transmitter electrode and thereceiver electrode based on the second demodulated output when theamount of interference exceeds a first amount. In one embodiment, thiscomprises demodulation type selector 435 selecting a type ofdemodulation which will be employed by processing system 110A when theamount of interference exceeds the first predetermined amount.Computation circuitry 445 then determines the measurement of a change intranscapacitive coupling (if any).

At 590 of flow diagram 500, in one embodiment, the measurement of changein transcapacitive coupling determined at 580 of flow diagram 500 isthen used by computation circuitry 445 in determining positionalinformation of an input object (if any) relative to sensing region 120.

Section 2 Shifting Carrier (Transmitter Signal) Frequency to AvoidInterference

FIG. 6 illustrates a display device and timing 600 comprising a displaywith a plurality of display rows 610 and their respective update times.In one embodiment, the physical row electrodes are used to sequentiallyupdate associated pixel from top to bottom of the display. The update ofpixels (or pixel color channels) is indicated front left to right. Inone embodiment, the common electrodes associated with plurality ofdisplay rows 610 at least partially overlap a sensing region of acapacitive sensor device. Also illustrated, according to an embodiment,is non-display update time 650 at the end of each pixel update time 640for a display pixel row, Non-display update time 650 is associated withupdating a display pixel row of the display device. Below display pixelrows 610, non-display update time 620 is also illustrated, according toan embodiment. As illustrated, line update time 630 is a sum of at leasta pixel update time 640 and non-display update time 650. Non-displayupdate time 650 may be referred to as horizontal blanking time ornon-update time and non-display update time 620 may be referred tovertical blanking time (lines or rows). In one embodiment, a non-displayupdate time associated with different rows may be different. Forexample, in one embodiment, the non-display update time associated withdifferent rows may be different to synchronize the display device withan external source. For example, the non-display update time between thelast row of a previous frame and the first row of a frame may be longerthan the non-display update time between the first and second rows of asingle frame.

The transmitter signal frequency (carrier signal frequency) of displaydevice 600 may be based on a relation of the display frame refresh rate(frame rate), number of display pixel rows 610, pixel update time 640,non-display update time 650, and the non-display update time 620.Further, even though FIG. 6 shows a non-display update time occurringafter the pixel row update time 640 for each display pixel row, in otherembodiments the non-display update time may occur at other times and/ormultiple non-display update times may occur on each display pixel row.In various embodiments, multiple pixels may be updated during a pixelrow update time. For example, a non-display update time may occur afterupdating each pixel channel (e.g. after updating each red, blue and/orgreen color channel) of a display pixel row. In various embodiments anon-display update time may vary from display pixel row to display pixelrow (e.g., first to second or last to first). In one embodiment, rowselection may comprise using transistors on the thin film transistor(TFT) glass selected (as a row) by the Display Driver Integrated.Controller (DDIC). The DDIC may be disposed on the TFT glass andelectrically coupled to the display pixel rows by Chip on Glass (COG)connections. In one embodiment, a separate flex (connected byanisotropic conductive film (ACF)) may carry signals to a hostprocessing system and to other elements of the processing system.

By varying the line update time 630, by adjusting the non-display updatetime 650, and/or by adjusting the number of vertical blanking lines, asynchronized transmitter signal frequency can be shifted or modulatedfor interference avoidance without varying the display frame refreshrate. In such an embodiment, the demodulation frequency or frequenciesmay be shifted similarly to the transmitter sigmal frequency whileachieving interference avoidance; various synchronization methods may beused to maintain the similarity. Synchronization signals that mayindicate horizontal row timing and vertical frame timing may be sharedand used for synchronization. Further, when multiple horizontal blankingtimes per display pixel row are used it is possible to vary the time ofeach individually. In a display device it is often desirable to maintainthe pixel update time 640 and display frame refresh rate to maintaindisplay quality (e.g., to avoid flickering, color shifting, or othervisually noticeable issues). Synchronization signaling between or withina processing system for the display device and a processing system for acapacitive sensor device can be used to maintain synchronization of thehorizontal refresh rate, control the length of the vertical blankingtime, manage requests for changing the transmitter signal frequency, orindications that a transmitter signal frequency may change. In oneembodiment, such synchronization is facilitated by utilizing a commonprocessing system to perform capacitive touch sensing and display updatein an integrated capacitive sensor device and display device. In anotherembodiment synchronized signals are shared between the capacitivesensing device and the display device. In one embodiment, the signalsmay be generated based on the display line or pixel timing of thedisplay. In one embodiment, the signals may be based on the frametimings of the display.

Consider an example where display device 600 has 800 display pixel rows610 with a pixel update time 640 of 15 μs per display pixel row and ahorizontal blanking time of about 5 μs per display pixel row. In such anembodiment the line update time is 20 μs, and corresponds to a Vcomcarrier frequency of about 25 KHz (e.g., for a line inversion methodwith ½ cycle per line). In this example, there are 10 vertical blankinglines, for a total of 810 rows. Therefore, the frame refresh rate is1/(810*20 μs) which is about 60 Hz. In one embodiment, additional linesmay be added or lines may be removed to synchronize the display to thevideo or image source.

To change the interference susceptibility of the capacitive sensor, thetransmitter signal, having a first frequency, can be shifted to a secondtransmitter signal having a second frequency, where the first and secondfrequencies differ. To shift from the transmitter signal having a firstfrequency to the second transmitter signal having a second frequency,the line update time 630, non-display update time 650, and numberanon-display update time 620 can be adjusted to maintain a constant orsubstantially constant frame refresh rate and constant pixel update time640 for each display pixel row. Following this example, for a 10 percenthigher transmitter signal frequency of 27.5 kHz the line update time 630is approximately 18 μs, and the shorter non-display update time 650 isapproximately 3 μs to keep the pixel update time 640 constant at 15 μsand to maintain a constant frame refresh rate of approximately 60 Hz.Therefore, to change the line update time 630, the non-display updatetime 650 and length (e.g., number of equivalent rows) of non-displayupdate time 620 will change, Based on the current example, for a displaydevice having 800 display rows and 10 vertical blanking lines and a lineupdate time of 20 μs, there are 810 total pixel rows (displayrows+vertical blanking lines) to be updated during a frame refresh ofthe display. For a line update time of 18 μs, 900 total pixel rows witha horizontal blanking time of 3 μs would be required, and since thenumber of display pixel rows 610 is constant based on the resolution ofthe display (800 pixel lines in this example) the length of verticalblanking time (e.g., number of equivalent lines) is increased from 10lines to 100 lines. Therefore, it would be possible to shift thefrequency of the transmitter signal and similarly shift the demodulationfrequency for interference avoidance, and in this example, provide anapproximately 10% line frequency shift without changing the framerefresh rate. In other embodiments, the line update time 630 and thenon-display update time 650 and the number of the non-display updatetime 620 can also be separately varied, also changing the interferencesusceptibility of the system. In another embodiment, multiplenon-display update times may occur in a single display frame withmultiple transitions during each non-display update time. In oneembodiment, a capacitive image may be measured to two separate verticalblanking times. The first vertical blanking time may be related to afirst fraction of the display frame pixel rows and the second verticalblanking time may be related to a second fraction of the display framepixel rows. The first and second fractions may be interlaced orcontiguous. In such embodiments, the capacitive measurement frame ratemay be at a rate different than the display frame rate.

In various embodiments, the length of the one or more of the verticalblanking lines may also be varied. In other embodiment, multipletransitions may be received and used to determine a change intranscapacitive coupling between transmitter and receiver electrodescaused by user input. In one embodiment, a signal may be shared betweena display device and a capacitive sensing device to indicate the changein the horizontal non-display update time or vertical blanking lines. Inone embodiment, the transmitter and demodulation frequencies can bechanged without altering a non-display update time. In one embodiment,the amount of time (e.g. duration) that a combination electrode istransmitting (and/or that a receiver electrode is receiving) during anon-display update time is changed (e.g., maintaining a constant numberof cycles but varying the frequency of the transmitter). In someembodiments, the spacing (e.g., duration) between measurements may bechanged. In various embodiments, multiple horizontal non-display updatetimes (horizontal blanking periods) may be changed. Further, transmittersignals may be transmitted on more than one combination electrode (orsets of combination electrodes) at substantially the same time. Thecombination electrodes may be spatially separate or adjacent to oneanother. In one embodiment, when multiple combination electrodes aredriven with transmitter signals, at least one transmitter signalcomprises transitions during a horizontal blanking period. In oneembodiment, transmitter signals that are driven on combinationelectrodes (or a set of combination electrodes) that are spatiallyseparated from the display pixel row being updated and may havetransitions that occur outside of the non-display update time, ratherthan exclusively during, a non-display update time.

Second Example Processing System

FIG. 7 illustrates a second example processing system 110B which may beutilized with an input device input device 100), according to variousembodiments. Processing system 110B may be implemented with one or moreASICs, one or more ICs, one or more controllers, or some combinationthereof. In one embodiment, processing system 110B is communicativelycoupled with a plurality of transmitter electrodes (or combinationelectrodes) and a plurality of receiver electrodes of sensing region 120of an input device 100. In one embodiment of input device 100,processing system 110B includes transmitter circuitry 405, receivercircuitry 415, and duration changer 755. Some embodiments additionallyinclude display update circuitry 765 and/or one or more of the othercomponents illustrated in processing system 110A of FIG. 4 (e.g.,computation circuitry 445).

Processing system 110B and the input device 100 of which it is apart aredisposed in and/or are communicatively coupled with an electronic system150, such as a display device (e.g., display device 600). In one suchintegrated embodiment, combination electrodes are utilized to supportboth display updating functions and capacitive sensing functions for atouch screen device that is integrated with the display of the displaydevice). Thus, the transmitter signals driven on these combinationelectrodes by transmitter circuitry 405 serve the purpose of bothdisplay updating and capacitive sensing. Overlaying and integrating thesensor pattern of FIG. 1B (combination electrodes 160 and receiverelectrodes 170) with the display pixel lines 610 of display device 600(FIG. 6) would be one example of such an embodiment. In otherembodiments, the receiver and transmitter electrodes are disposed abovethe display electrodes (e.g., on the color filter glass, display lens oranother substrate of the display or external to the display) and thetransmitter electrodes may not be part of the display device and are notthe combination electrodes, but the transmitter electrodes may still besynchronized with the display.

Transmitter circuitry 405 may operate to drive a transmitter signal onone or more transmitter or combination electrodes that are disposed in asensing region/display. In a given time interval, transmitter circuitry405 may drive a transmitter signal (waveform) on one or more of aplurality of combination electrodes. In one embodiment, the transmittersignal has a first frequency. In one embodiment, the time interval forwhich the same set of (or group of) combination electrodes are drivenmay be one half cycle (single transition) and one non-display updatetime or it may be for multiple (halt) cycles and multiple Bon-displayupdate times. In one embodiment, the spatial selection of selectedcombination electrodes may scan in an overlapping manner, where asegment of a segmented Vcom electrode of the combination electrode setmay be driven in two consecutive non-display times. In anotherembodiment the spatial selection of selected combination electrodes mayscan in a non-overlapping manner, where a segment of a segmented Vcomelectrode of the combination electrode may be driven during a firstnon-display update time and not during a consecutive non-display updatetime. In one embodiment, a set of forty combination electrodes (e.g., ablock of combination electrodes) may be driven thr nigh two duty cycles(e.g., in twenty row times) and in a subsequent twenty cycles adifferent non-overlapping set of combination electrodes (e.g., adifferent block) may be driven. Different numbers of combinationelectrodes may form each set and combination electrodes and differentcombination electrodes within a set may be driven at differentpolarities. In one embodiment, different numbers of combinationelectrodes may form each set and combination electrodes and differentcombination electrodes within a set may be driven may be driven withdifferent voltages. In such embodiments, the signals from the set aresimilarly modulated and demodulated as a set.

In another embodiment, a set of twenty combination electrodes may bedriven through one half of a cycle and then a new overlapping set ofcombination electrodes is driven. The second set of combinationelectrodes is incremented by one combination electrode, where all butone combination electrode overlaps. In other embodiments, the sets maybe incremented by other amounts so that different numbers of combinationelectrodes overlap.

In one embodiment, the combination electrodes may be directly coupled tothe processing system 110 or DDIC or connected through selection andarbitration transistors. The electrodes may be coupled at different ormultiple points (e.g., at a left end, right end or on both ends) to thetransmitter circuitry of the processing system 110. The transmittersignal may be a square wave, trapezoidal wave, or some other waveform.Waveforms 910, 920, and 930 of FIG. 9 illustrate some examples oftransmitter signals which may be transmitted by transmitter circuitry405. It should be noted, and will be further explained below, thatwaveforms 910, 920, and 930 illustrate that multiple transitions (e.g.,two or more) can be made in the waveform of the transmitted transmittersignal and timed such that the transitions occur during a non-displayupdate time period (e.g., horizontal blanking period or verticalblanking period). During a blanking period, the transitions will have aminimal effect upon display updating, but can provide sufficienttransitions for sampling (e.g., demodulating) for touch sensing.

Receiver circuitry 415 operates to receive resulting signals, viareceiver electrodes that correspond to the transmitted transmittersignals (e.g., transitions). The received resulting signals correspondto and may include some version of the transmitter signal(s) transmittedvia the transmitter electrodes. These transmitted transmitter signalshowever, may be altered or changed in the resulting signal due to straycapacitance, interference (noise), and/or circuit imperfections amongother factors, and thus may differ slightly or significantly from theirtransmitted versions. Demodulation of resulting signals corresponding todifferent sets of driven transmitter electrodes (combination electrodes)may comprise different timings (e.g., delayed or lengthened integrationand sampling) or alternatively they may all be substantially similar.Resulting signals may be received on one or a plurality of receiverelectrodes during a time interval. In one embodiment, in a low powermode, fewer receiver electrodes may be used FIGS. 3A-3D illustratesampling of resulting signals which are received by receiver circuitry415. In one embodiment, the resulting signals may also be altered due tothe effect of user input on the coupling capacitance.

Duration changer 755 may operate to change a duration of at least onenon-display update time period, of a display device. This can be achange in one or more of the horizontal blanking time or the number ofvertical blanking lines (or duration of the vertical blanking time). Inone embodiment, the change in duration is initiated by duration changer755 based on an amount of interference. For example, duration changer755 can measure and compare amounts of interference in any of themanners described in conjunction with demodulation type selector 435,including measuring ambient interference. The change in duration causesa shift from transmitting the first transmitter signal with thecombination electrode to transmitting a second transmitter signal thecombination electrode. The second transmitter signal has a secondfrequency that is different from the first frequency of the firsttransmitter signal. The change in duration does not substantially changea refresh rate of the display device. By “not substantially,” What ismeant is that the refresh rate is maintained within a window plus orminus a small percentage of the refresh rate, which does not visiblyalter viewing to a human viewer of the display device, and minimaleffect on any image/video synchronization. In one embodiment, durationchanger 755 may operate to change the length of time that the resultingsignals are demodulated or change the length of time between demodulatedsets of resulting signals (e.g., resulting signals corresponding tocombination electrodes driven during a vertical blanking time). Invarious embodiments, the resulting signals may be demodulated fordifferent durations and/or for different frequencies to maintain aconstant number of demodulation cycles.

In one embodiment, duration changer 755 changes the duration of the atleast one non-display update time period by increasing duration of anon-display update time period (e.g., increasing the length of ahorizontal blanking time or increasing the number of vertical blankinglines associated with updating a pixel display row (or frame) of thedisplay device. In one embodiment, duration changer 755 changes theduration of the at least one non-display update time period bydecreasing duration of a non-display update time period (e.g.,decreasing the length of a horizontal blanking time or decreasing thenumber of vertical blanking lines) associated with updating a pixeldisplay row of the display device. In one embodiment, by monitored LCDsignals (e.g., Tear Enable (TE) horizontal row timing signals orvertical frame timing signals) may be used to detect, predict and changethe horizontal blanking times and vertical blanking times used fortransmitting.

Display update circuitry 765 operates to perform display updatingfunctions by using the first transmitter signal and the secondtransmitter signal as display update signals for updating the displaydevice. For example, the first and second transmitter signals can betransmitted with a combination electrode that is being utilized toupdate the display device and simultaneously being used as a transmitterelectrode of a capacitive sensor device.

Example Method of Avoiding Interference in an Integrated CapacitiveSensor and Display Device

FIG. 8 illustrates a flow diagram 800 of an example method of avoidinginterference in an integrated capacitive sensor device and displaydevice, according to various embodiments. For purposes of illustration,reference will be made to components of processing system 110B of FIG. 7in the description of flow diagram 800. In some embodiments, not all ofthe procedures described in flow diagram 800 are implemented. In someembodiments, other procedures in addition to those described may beimplemented. In some embodiments, procedures described in flow diagram800 may be implemented in a different order than illustrated and/ordescribed.

At 810 of flow diagram 800, in one embodiment, a first transmittersignal is transmitted with a combination electrode of an integratedcapacitive sensor device and display device. The combination electrodeis configured for both capacitive sensing and display updating. Thefirst transmitter signal has a first frequency. In one embodiment,transmitter circuitry 405 drives the first transmitter signal that istransmitted with the combination electrode.

At 820 of flow diagram 800, in one embodiment, a shift is made fromtransmitting the first transmitter signal with the combination electrodeto transmitting a second transmitter signal with the combinationelectrode. In one embodiment, transmitter circuitry 405 drives the firsttransmitter signal. In one embodiment, the shift is carried out byduration changer 755 in a manner previously described. The shiftinvolves changing a duration of at least one non-display update timeperiod of the display device (e.g., altering one or more horizontalblanking times or varying the number or duration of vertical blankinglines). In one embodiment, the shift comprises changing the length timethat a set of combination electrodes are driven to measure a change incapacitance or changing the time between driven sets of combinationelectrodes. For example, duration changer 755 can increase or decreaseduration of a non-display update time period (e.g., one or morehorizontal blanking times or vertical blanking lines) associated withupdating a row of the display device. The second transmitter signal hasa second frequency which is different from the first frequency. In someembodiments, the repeat period of the transmitter modulation or thecycle time of the modulation is different or the pulse width isdifferent. The shifting occurs based, at least in part, upon an amountof interference and does not substantially change the refresh rate ofthe display device. That is, in some embodiments, the frame refresh ratewill not change at all, or else may change by some small amount which isnot noticeably perceptible to a human viewer of the display device. Itis possible to affect a greater change than this to the refresh ratebetween the first and the second transmitter signal, however, a largechange should be weighed against any possible negative visual impact itmay cause for a user/viewer of a display device or with video or imagesynchronization with the device.

The first and second transmitter signals are waveforms, such as a squarewaves, trapezoidal waves, or other waveforms. In some embodiments,either or both of the first and second transmitter signals is/aretransmitted and timed such that the signal(s) include(s) two or moretransitions that occur during a non-display update time periodassociated with updating a row of a display device in which thetransmitter signals are being used.

At 830, in one embodiment, the method of flow diagram 800 furtherincludes a procedure of using the first transmitter signal for some partof the signal period, to update the display device. In one embodiment,for example, display update circuitry 765 operates to perform displayupdating functions by using both the first transmitter signal and thesecond transmitter signal as display update signals for updating thedisplay device. For example, the first and second transmitter signalscan be transmitted with a combination electrode that is being utilizedto update a display device and simultaneously being used as atransmitter electrode of a capacitive sensor device (e.g., for a lineinversion display). In one embodiment, the first and second transmittersignals may be utilized to update a display device for some portion ofthe display frame and be utilized to transmit during a non-displayupdate time (e.g., for a DC Vcom dot-inversion display).

At 840, in one embodiment, the method of flow diagram 800 furtherincludes a procedure of receiving a resulting signal with a receiverelectrode, where the resulting signal corresponds to the firsttransmitter signal. In one embodiment, for example, the resulting signalcan be received by receiver electrode and communicatively coupled withcircuitry 415. In other embodiments, a receiver electrode may alsoreceive resulting signals when no transmitter signal is transmitted tomeasure interference.

At 850, in one embodiment, a first measurement is determined of a changein a transcapacitive coupling between the combination electrode and thereceiver electrode. This first measurement is determined based on theresulting signal that is received in procedure 840. For example,computation circuitry 445 can determine the measurement of a change intranscapacitive coupling (if any).

At 860, in one embodiment, positional information is determined. Thispositional information is determined based on the first measurement ofprocedure 860. For example, computation circuitry 445 can determinepositional information of an input object (if any) relative to sensingregion 120.

Section 3 Sensing During Display Non-Display Update Time to AvoidInterference

In some embodiments, the transmitter signal may be transitioned morethan once before pixel row updates during the non-display update time(e.g., horizontal blanking period or vertical blanking period) toimprove the signal to noise ratio and interference susceptibility. Inother embodiments, a non-display update time may occur between rowupdates of a display line and/or at other times. In various embodiments,display frames may be updated progressively or interlaced (e.g., duringa first display frame a first half or fraction of the display is updatedand during a second display frame a second half or fraction of thedisplay is updated and where the two halves or fractions areinterlaced). In one embodiment, a first non-display update time isassociated with updating a first pixel row of a display frame and asecond non-display update time is associated with updating a secondpixel row of a display frame. In one embodiment, a first non-displayupdate time is associated with updating a first interlaced fraction of adisplay frame and a second non-display update time is associated with asecond interlaced fraction of the display frame. In one embodiment, thesame non-display update times are repeated at the frame rate (or afraction of the frame rate and any variations in the non-display updatetimes are made at the smallest spatial separation to minimize visibleeffects.

FIG. 9 illustrates three transmitter signals 910, 920, and 930 withtransitions during non-display update time, according to variousembodiments. In FIG. 9, transmitter signal 910 has two transitions,transmitter signal 920 has three transitions, and transmitter signal 930has four transitions. Each of these transmitter signals 910, 920, 930has the transitions timed such that they occur during a non-displayupdate time associated with a display row (e.g., prior line update timeor post line update time as shown in FIG. 9). In various embodiments,the transmitter signals 910, 920, 930 may have an average output equalto half of the peak amplitude (e.g., ((Vcom+)+Vcom−)/2). Maintaining anaverage voltage near ((Vcom+)+Vcom−)/2) can contribute positively to thedisplay quality. In one embodiment, the average Vcom voltage is a DCVcom voltage.

FIG. 9 shows that the double transition transmitter signal 910, thetriple transition transmitter signal 920, and the quadruple transitiontransmitter signal 930 can provide two or more signal sample pairs. Inother embodiments, other number of transitions may also be used. In someembodiments, more than four transitions may be used and more than oneset of electrodes may be scanned. In one embodiment, more than 20transitions may be used. Transmitter signals (e.g., 920) with oddnumbers of transitions would (typically) be used when a display isscanned using line inversion (the Vcom voltage alternates between twovoltages when scanning pixel display rows). Transmitter signals (e.g.,910, 930) with even numbers of transitions such as 2, 4, 6 or moretransitions would (typically) be used when a display is scanned usingdot inversion (the Vcom voltage returns to a constant voltage whenscanning pixel display rows). Both the positive and negative samples maybe demodulated even when there is only a single transition, or fewersamples can be used (e.g., only two samples of opposite or the samepolarity) even when more transitions occur (e.g., three or four and notall transition amplitudes need to be the same. Double sampling allowsfor non-overlapping susceptibility curves as described above. In anotherembodiment, a change in duration may change the duration of thetransitions during more than one Bon-display update in a display frame.In such an embodiment, the number of demodulated transitions can bemaintained constant at a different sensing frequency.

In one embodiment, the maximum number of effective transitionscorresponds to the settling time of the combination electrodes. Further,in other embodiment, the maximum amount of time for updating the pixelsalso corresponds to the settling time of the combination electrode. Inother embodiments, as the settling times for the combination electrodesare improved (e.g., shortened), the number of transitions and/or amountof non-display update time may be increased. In one embodiment, thesettling time for the combination electrodes may be improved by couplingeach combination electrode to one or more low impedance drivers at oneor more locations along the length of the combination electrode.Further, in other embodiments, the settling time of the receiverelectrodes may be improved by coupling processing system 110 at morethan one location along the length of each receiver electrode,increasing the thickness and/or width of each receiver electrode, usingadditional low resistance materials or using any other means to reducethe resistance or capacitance of each receiver electrode.

Third Example Processing System

FIG. 10 illustrates a third example processing system 110C which may beutilized with an input device (e.g., input device 100), according tovarious embodiments. Processing system 110C may be implemented with oneor more ASICs, one or more ICs, one or more controllers, or somecombination thereof. In one embodiment, processing system 110C iscommunicatively coupled with a plurality of combination electrodes and aplurality of receiver electrodes of sensing region 120 of an inputdevice 100. In one embodiment of input device 100, processing system110C includes transmitter circuitry 405 and receiver circuitry 415. Someembodiments additionally include one or more of demodulation circuitry425, demodulation type selector 435, computation circuitry 445, durationchanger 755, and/or display update circuitry 765.

Processing system 110C and the input device 100 of which it is a partare disposed in and/or are communicatively coupled with an electronicsystem 150, such as a display device (e.g., display device 600). In onesuch integrated embodiment, combination electrodes are utilized tosupport both display updating functions and capacitive sensing functions(e.g., for a capacitive sensing device that is integrated with thedisplay of the display device). Thus, the transmitter signals driven onthese combination electrodes by transmitter circuitry 405 serve thepurpose of both display updating and touch sensing. Overlaying andintegrating the sensor pattern of FIG. 1B (combination electrodes 160and receiver electrodes 170) with the display pixel lines of a displaydevice would be one example of such an embodiment.

Transmitter circuitry 405 operates to drive a transmitter signal that istransmitted with a combination electrode of an integrated capacitivesensor device and display device. The transmitter signal is transmittedwith a low impedance transmitter during both a display update timeperiod and also during a non-display update time period that isassociated with row update of the display device. In one embodiment, forexample, transmitter circuitry 405 drives a transmitter signal, such astransmitter signal 920 of FIG. 9, where the transmitter signaltransitions at least two times during the non-display update time periodassociated with row update of the display device (e.g., during thehorizontal blanking time after a display row or during vertical blankingtime after the last display row updated in a frame), in one embodiment,transmitter circuitry 105 is configured to simultaneously transmit on aplurality of combination electrodes (e.g., a plurality of pixel rows).

Receiver circuitry 415 operates to receive a resulting signal with areceiver electrode during the non-display update time period (e.g.,during the horizontal blanking period when the transitions are takingplace). The resulting signal corresponds to the transmitter signal, ashas been previously described, but may include interference (noise), orother inputs in addition to some or all content of the transmittedtransmitter signal. In one embodiment, the transmitted transmittersignal may be associated with more than one display row update. In oneembodiment, a sequence of twenty row updates occurs while the same setof twenty combination electrodes are driven with a similar modulation.

In one embodiment, processing system 110C determines a first measurementof a transcapacitive coupling between the combination electrode (orcombination electrode set) and the receiver electrode corresponds to theresulting signal and uses this first measurement of transcapacitivecoupling in determining positional information of an input object (ifany) relative to sensing region 120. In one embodiment, these functionsare performed by computation circuitry 445, if included in processingsystem 110C.

in one embodiment, processing system 110C transmits a display updatesignal for the display device portion of the integrated capacitivesensor and display device. The display update signal is transmitted withpixel update electrodes coupled to the combination electrode. In oneembodiment, this function is carried out by display update circuitry765, if included in processing system 110C. In one embodiment, asynchronization pulse is communicated between a discrete capacitivesensing device and a discrete display device. In one embodiment, thesynchronized signal is based on the phase of the display frame. Invarious embodiments, the synchronized signal is based on a display pixelrow being updated, frame periods or multiples of the frame periods. Inone embodiment, the clock frequency may be shared between the capacitivesensing device and a display device. The clock frequency may include apixel clock or a divided pixel clock.

In one embodiment, processing system 110C includes demodulationcircuitry 425 which, as previously described in conjunction with FIG. 4and processing system 110A, can: acquire a first demodulated output bydemodulating the resulting signal in a first way; and acquire a seconddemodulated output by demodulating the resulting signal in a second waythat is different from the first way of demodulating the resultingsignal.

In one embodiment, processing system 110C includes demodulation typeselector 435 which, as previously described in conjunction with FIG. 4and processing system 110A, can shift the demodulation circuitry fromusing the first demodulated output for determining positionalinformation to using the second demodulated output for determiningpositional information. The shift can be based, at least in part, uponan amount of interference that is detected by processing system 110C inone or more demodulated outputs.

In one embodiment, processing system 110C includes duration changer 755which, as previously described in conjunction with FIG. 7 and processingsystem 110B, can: change a duration of at least one non-display updatetime period of a display device. This can be a change in one or more ofthe horizontal blanking time or the period of vertical blanking lines.In one embodiment, the change in duration is initiated by durationchanger 755 based on an amount of interference. In another embodiment,the change in duration is initiated by a synchronization signal (e.g.,between a capacitive sensing processing system and a display driver).For example, duration changer 755 can measure and compare amounts ofinterference in any of the manners described in conjunction withdemodulation type selector 435, including measurements of ambientinterference. The change in duration causes a shift from transmittingthe first transmitter signal with the combination electrode totransmitting a second transmitter signal with the combination electrode.The second transmitter signal has a second frequency that is differentfrom the first frequency of the first transmitter signal. The change induration does not substantially change a refresh rate of the displaydevice. By “not substantially,” what is meant is that the refresh rateis maintained within a window of plus or minus a one Hertz in oneembodiment. The window may be smaller, such as plus or minus 0.5 Hertz,or larger such as plus or minus 3 Hertz. In various embodiments, thedisplay frame refresh rate may be controlled and synchronized with thedisplay image or video source. In one such embodiment, this may changethe duration of different non-display update times within a frame on aframe by frame basis.

Example Method of Sensing Using an Integrated Capacitive Sensor Deviceand Display Device

FIGS. 11A-11C illustrate a flow diagram 1100 of an example method ofcapacitive sensing using an integrated capacitive sensor device anddisplay device, according to various embodiments. For purposes ofillustration, reference will be made to components of processing system110C of FIG. 10 in the description of flow diagram 1100. In someembodiments, not all of the procedures described in flow diagram 1100are implemented. In some embodiments, other procedures in addition tothose described may be implemented. In some embodiments, proceduresdescribed in flow diagram 1100 may be implemented in a different orderthan illustrated and/or described.

At 1110 of flow diagram 1100, in one embodiment, a first transmittersignal is transmitted with a combination electrode of an integratedcapacitive sensor device and display device. The combination electrodeis configured for both capacitive sensing and display updating. Thefirst transmitter signal has a first frequency and transitions at leasttwice to at least two different signal voltages during a non-displayupdate time period associated with row update of the display device (seee.g., transmitter signal 910, 920, and 930 of FIG. 9). In oneembodiment, transmitter circuitry 405 drives the first transmittersignal which is transmitted with the combination electrode. The firsttransmitter signal may act as a display update signal for updating adisplay portion of the integrated capacitive sensor device and displaydevice for a portion of the frame times. In one embodiment, transmittercircuitry 405 drives a second transmitted transmitter signal that isassociated with a second row during a non-display update time.

At 1120 of flow diagram 1100, in one embodiment, the pixels in a displayof the display device are updated during an update time period. In oneembodiment, display update circuitry 765 performs this updating while atransmitter signal is being transmitted during pixel update time (seee.g., pixel update time 640 of FIG. 6).

At 1130 of flow diagram 1100, in one embodiment, a resulting signal isreceived with a receiver electrode of the integrated, capacitive sensordevice and display device during the non-display update time period. Asdescribed previously, the resulting signal corresponds to the firsttransmitter signal. In one embodiment, the resulting signal is receivedby receiver circuitry 415 in any of the manners previously describedherein.

At 1140, in one embodiment, the method of flow diagram 1100 furtherincludes a procedure of determining a first measurement of a change in atranscapacitive coupling between the combination electrode (or set ofcombination electrodes) and the receiver electrode based on theresulting signal. In one embodiment, computation circuitry 455determines this first measurement of a change in transcapacitivecoupling.

At 1150 of flow diagram 1100, in one embodiment, the method determinespositional information (if any) of an input object relative to a sensingregion based on the first measurement of change in a transcapacitivecoupling that was determined at 1140. In one embodiment, this positionalinformation determination function is also carried out by computationcircuitry 455.

At 530, in one embodiment, the method of flow diagram 1100 furtherincludes a procedure of acquiring a first demodulated output bydemodulating the resulting signal in a first way. In one embodiment,demodulation circuitry 425 acquires this first demodulated output bydemodulating the resulting signal in a first way of a plurality ofdifferent ways that it is capable of demodulating.

At 540 of flow diagram 1100, in one embodiment, a second demodulatedoutput is acquired by demodulating the resulting signal in a second way,where the second way and the first way differ from one another. In oneembodiment, demodulation circuitry 425 acquires this second demodulatedoutput by demodulating the resulting signal in a second way of aplurality of different ways that it is capable of demodulating. It isappreciated that the first and second way of demodulation may bedifferent because samples are weighted differently in the second waythan the first way; because samples are sampled in a different phase inthe second way than in the first way; because a different number ofsamples is used in the second way than in the first way; and/or becausethe second way utilizes one or more different time spans between samplesthan the first way.

At 550 of flow diagram 1100, in one embodiment, the method shifts fromusing the first demodulated output for determining positionalinformation to using the second demodulated output for determiningpositional information. The shift is based, at least in part, upon anamount of interference. In one embodiment, demodulation type selector435 determines when and to what type of demodulation to shift. In oneembodiment, the amount of interference is based on a measurement ofinterference in first demodulated output. In one embodiment, the amountof interference is based on a measurement of interference in the seconddemodulated output. Amounts can be compared to one another or to apredetermined scale. In one embodiment, the amount of interference is ameasure of ambient/environmental (non-sensor) interference during a timewhen no transmitter signals are being transmitted by transmittercircuitry 405. For example, receiver circuitry 415 receives a secondresulting signal from a receiver electrode during a time period when notransmitter signal is transmitted with any combination electrode bytransmitter circuitry 405. In one embodiment, demodulation circuitry 425acquires a third demodulated output by demodulating this secondresulting signal in one of the first and second ways and determining anamount of interference that exists in this third demodulated output.This amount of interference from the third demodulated output is thenused as a basis for selecting among the plurality of different types ofdemodulation (e.g., first type, second type, etc.) to use.

At 820, in one embodiment, the method of flow diagram 1100 furtherincludes the procedure of shifting from transmitting the firsttransmitter signal with the combination electrode to transmitting asecond transmitter signal with the combination electrode. In oneembodiment, transmitter circuitry 405 drives the first transmittersignal. In one embodiment, the shift is carried out by duration changer755 in the manner previously described. The shift involves changing aduration of at least one non-display update time period of the displaydevice (e.g., altering one or more horizontal blanking times or varyingthe number of vertical blanking lines) or one transmitter durationduring a non-display update time (e.g., the time transmitting on acombination electrode or the time between transmissions). For example,duration changer 755 can increase or decrease duration of a non-displayupdate time period (e.g., one or more horizontal blanking times)associated with updating a row of the display device. The secondtransmitter signal has a second frequency which is different from thefirst frequency. The shifting occurs based, at least in part, upon anamount of interference and does not substantially change the refreshrate of the display device. That is, in some embodiments, the refreshrate will not change at all, or else may change by some small percentagethat is not noticeably perceptible to a human viewer of the displaydevice. In one example, the refresh rate may change by some amount thatis less than 1 Hz. It is possible to affect a greater change than thisto the refresh rate with the second transmitter signal, however, such achange should be weighed against any negative visual impact it may causefor a user/viewer of a display device. In another embodiment, theduration of transmitting a transmitter signal is changed on a firstcombination electrode. In a further embodiment, the duration oftransmitting a transmitter signal in a second combination electrode ischanged. In yet another embodiment, the first and second combinationelectrodes are modulated simultaneously.

The first and second transmitter signals are waveforms, such as a squarewaves, trapezoidal waves, or other waveforms. In some embodiments,either or both of the first and second transmitter signals is/aretransmitted and timed such that the signal(s) include(s) two or moretransitions that occur during a non-display update time periodassociated with updating a first portion of a display device (e.g., afirst pixel row or set of rows) in which the transmitter signals arebeing used. In some embodiments, the first and second transmittersignals are associated with updating a second portion of a displaydevice (e.g., a second pixel row or set of rows) in which thetransmitter signals are being used.

In one embodiment, the method of flow diagram 1100 further includesusing the first transmitter signal to update the display device. In oneembodiment, for example, display update circuitry 765 operates toperform display updating functions by using the first transmitter signaland the second electrical as display update signals for updating thedisplay device. For example, the first and second transmitter signalscan be transmitted with a combination electrode that is being utilizedto update a display device and simultaneously being used as atransmitter electrode of a capacitive sensor device.

Thus, the embodiments and examples set forth herein were presented inorder to best explain the present invention and its particularapplication and to thereby enable those skilled in the art to make anduse the invention. However, those skilled in the art will recognize thatthe foregoing description and examples have been presented for thepurposes of illustration and example only. The description as set forthis not intended to be exhaustive or to limit the invention to theprecise form disclosed.

1. A method of interference avoidance for a capacitive sensor device,said method comprising: transmitting a transmitter signal with atransmitter electrode of said capacitive sensor device; receiving aresulting signal with a receiver electrode of said capacitive sensordevice, said resulting signal corresponds to said transmitter signal;acquiring a first demodulated output by demodulating said resultingsignal in a first way; acquiring a second demodulated output bydemodulating said resulting signal in a second way, wherein said secondway and said first way differ; and shifting from using said firstdemodulated output for determining positional information to using saidsecond demodulated output for determining positional information,wherein said shifting is based at least in part upon an amount ofinterference.
 2. The method as recited in claim 1, further comprising:determining a measurement of a change in transcapacitive couplingbetween said transmitter electrode and said receiver electrode based onsaid first demodulated output when said amount of interference is lessthan a first amount; and using said measurement in determining saidpositional information.
 3. The method as recited in claim 1, furthercomprising: determining a measurement of a change in transcapacitivecoupling between said transmitter electrode and said receiver electrodebased on said second demodulated output when said amount of interferenceexceeds a first amount; and using said measurement in determining saidpositional information.
 4. The method as recited in claim 1, whereinsaid transmitting a transmitter signal with a transmitter electrodecomprises: transmitting said transmitter signal such that saidtransmitter signal comprises at least two transitions that occur duringa non-display update time period associated with updating a row of adisplay device, wherein said display device at least partially overlapsa sensing region of said capacitive sensor device.
 5. The method asrecited in claim 1, wherein said demodulating said resulting signal in asecond way comprises: weighting samples differently than said first way.6. The method as recited in claim 1, wherein said demodulating saidresulting signal in a second way comprises: sampling in a differentphase than said first way.
 7. The method as recited in claim 1, whereinsaid demodulating said resulting signal in a second way comprises:utilizing a different number of samples than said first way.
 8. Themethod as recited in claim 1, wherein said demodulating said resultingsignal second way comprises: utilizing a different time span samplesthan said first way.
 9. The method as recited in claim 1, wherein saidshifting from using said first demodulated output for determiningpositional information to using said second demodulated output fordetermining positional information comprises: shifting from using saidfirst demodulated output to using said second demodulated output basedat least in part upon said amount of interference, wherein said amountof interference is based on a measurement of said first demodulatedoutput.
 10. The method as recited in claim 1, wherein said shifting fromusing said first demodulated output for determining positionalinformation to using said second demodulated output for determiningpositional information comprises: shifting from using said firstdemodulated output to using said second demodulated output based atleast in part upon said amount of interference, wherein said amount ofinterference is based on a measurement of said second demodulatedoutput.
 11. The method as recited in claim 1, wherein said shifting fromusing said first demodulated output for determining positionalinformation to using said second demodulated output for determiningpositional information comprises: shifting from using said firstdemodulated output to using said second demodulated output based atleast in part upon said amount of interference, wherein said amount ofinterference is based on a measurement of a third demodulated output,wherein said third demodulated output is acquired by demodulating asecond resulting signal in one of said first and second ways, and wheresaid second resulting signal is received by said receiver electrodeduring a time period when no transmitter signal is transmitted with saidtransmitter electrode.
 12. A processing system communicatively coupledwith a capacitive sensor device and a display device, said processingsystem comprising: transmitter circuitry configured to transmit atransmitter signal with a transmitter electrode of said capacitivesensor device; receiver circuitry configured to receive a resultingsignal with a receiver electrode of said capacitive sensor device, saidresulting signal corresponds to said transmitter signal; demodulationcircuitry configured to: acquire a first demodulated output bydemodulating said resulting signal in a first way; and acquire a seconddemodulated output by demodulating said resulting signal in a secondway, wherein said second way and said first way differ; and ademodulation type selector configured to shift said demodulationcircuitry from using said first demodulated output for determiningpositional information to using said second demodulated output fordetermining positional information, wherein said shift is based at leastin part upon an amount of interference.
 13. The processing system ofclaim 12, further comprising computation circuitry configured to:determine a measurement of a change in transcapacitive coupling betweensaid transmitter electrode and said receiver electrode based on saidfirst demodulated output when said amount of interference does notexceed a first amount; and utilize said measurement in determining saidpositional information.
 14. The processing system of claim 12, furthercomprising computation circuitry configured to: determine a measurementof a change in transcapacitive coupling between said transmitterelectrode and said receiver electrode based on said second demodulatedoutput when said amount of interference exceeds a first amount; andutilize said measurement in determining said positional information. 15.The processing system of claim 12, wherein said demodulation circuitryconfigured to acquire a second demodulated output by demodulating saidresulting signal in a second way comprises: said demodulation circuitrybeing configured to weight samples differently than said first way. 16.The processing system of claim 12, wherein said demodulation circuitryconfigured to acquire a second demodulated output by demodulating saidresulting signal in a second way comprises: said demodulation circuitrybeing configured to sample in a different phase than said first way. 17.The processing system of claim 12, wherein said demodulation circuitryconfigured to acquire a second demodulated output by demodulating saidresulting signal in a second way comprises: said demodulation circuitrybeing configured to utilize a different number of samples than saidfirst way.
 18. The processing system of claim 12, wherein saiddemodulation circuitry configured to acquire a second demodulated outputby demodulating said resulting signal in a second way comprises: saiddemodulation circuitry being configured to utilize a different time spanbetween samples than said first way.
 19. An input device comprising: adisplay device, said display device comprising a combination electrodeconfigured for both display updating and touch sensing; a receiverelectrode of a capacitive sensing device, said receiver electrodedisposed proximate said combination electrode and configured for touchsensing; and a processing system communicatively coupled with saidcombination electrode and said receiver electrode, said processingsystem configured to: transmit a transmitter signal with saidcombination electrode; receive a resulting signal with a receiverelectrode of said capacitive sensor device, said resulting signalcorresponds to said transmitter signal; acquire a first demodulatedoutput by demodulating said resulting signal in a first way; and acquirea second demodulated output by demodulating said resulting signal in asecond way, wherein said second way and said first way differ; and shiftfrom using said first demodulated output for determining positionalinformation to using said second demodulated output for determiningpositional information, wherein said shift is based at least in partupon an amount of interference.
 20. The input device of claim 19,wherein said processing system is further configured to: determine afirst measurement of a change in transcapacitive coupling between saidcombination electrode and said receiver electrode based on said firstdemodulated output when said amount of interference does not exceed afirst amount; determine a second measurement of a change intranscapacitive coupling between said combination electrode and saidreceiver electrode based on said second demodulated output when saidamount of interference exceeds said first amount; and utilize one ofsaid first and said second measurement in determining said positionalinformation.